Well it comes down to this i dont see a guide on here that fits my play style, and from what i can tell from solo ranked and non ranked alike this build/play style works really well! so time for the sharing(and healing) to begin.

side note here:Their are a number of other item builds that can work really well for end game but the first 3 items i highly recommend that order for, and it will be explained why later in the guide.

side note 2: yes it seems crazy on my spells but again they WILL be explained. but they ARE for a very specific play style if you dont/cant play that way then DO NOT use them as they will not give you the proper advantage.

Pro's:
1. Amazing lane pusher, especially for mid but still works great in side lanes
2. Early-mid game domination, but still scales well for late game as a harasser
3. played correctly you can be mia from your own lane a lot for harrasment/kills in other lanes because you WILL force your lane to go back to base.
4. summoner spells help alleviate some/most of the cons used correctly.

Con's:
1. You are playing the roll of a harasser, this means you will have take some damage, and use all your mana, so you will have to go back to base a lot. the bright side:playing your harassment right(which takes some practice) you can time your pills to be in line with your lanes enemy deaths/pills AND always be able to afford at least 1 more item(partial or full)
2. If your opponent is very experienced with/against caitlyn this can stop your lane pushing in its tracks. more on this covered later.
3. Late game you will do decent damage but most 1v1 fights you loose, you need your team.

I will say this their are any number of viable rune builds for caitlyn my rune choices are their for a few reasons:
1. They are the best ip/what you get ratio, in other words not only is the rune cheaper than many of the alternatives but you get more from it than a more expensive rune.
2. i am poor! feel free if you dont have the runes, or want to change them up some to do so! just keep in mind these pointers

DO:
Armor pen: stacking close to or even over initial starting armor is a MUST for harassment, you want to maximize the damage dealt.
Attack speed:very important allows more certainty of last hits on minions
Physical damage: gives a nice solid edge early/mid game most champs i see concentrate way to much on this and not enough on armour pen, so even though they go into the fight with "higher" initial damage im still doing more damage to them then they do to me simply because of armour pen.

DONT:
mana/life: just no, yes she will run out of mana, yes she will get hurt, but thats what your spells are their for. base buy an item continue harassment.
Crit strike/greater crit: Caitlyn is not about critical till late game, meaning your giving up a LOT of early game power in your lane as her abilities scale off pure AD damage.
CD reduction: Cait already has relatively low cool downs on her abilities, and again you give up damage for this, not worth it
Any other runes: just not worth it, that simple.

This section i really have little to say about, 21-0-9 is rather standard only big difference for me is that point in ghost, if you choose not to use ghost then place it somewhere else. everything else on this is very standard for most AD champs.

How to piltover:

Attacker:
Each game is different on this, so your most important task is to send a couple piltovers directly at your opponent and judge how/if he(or she) is dodging them. Most players that do dodge tend to favor one side(right or left dodge) if you know they are likely to dodge to the left then lead some with the shot this way they dodge INTO it. Also a great way to ensure your piltovers land is to wait for them to close for a last hit, so watch your minions as well, when you see an opponent going for a last hit line up where they will be at for it and let loose. same goes for if they are closing for an ability.

Many people(good players) with ranged abilities will duck in and out a few times before coming in close enough to actually launch an ability, they are trying to bait your piltover, so let them move in and out a time or two so that you know when they have already clicked forward this way they are running into the shot and have a much harder time dodging it. against players NOT using this tactic and just rushing in to launch abilities then go ahead and launch piltover as soon as you see them running at you. you can then A. auto attack them for additional damage as they launch whatever ability or B. 90 caliber net out of range of their ability, i dont recommend this as much because it wastes mana.

IMPORTANT!:Dont be popping off this ability JUST to farm minions early game use it ONLY when you have a reasonably good chance of hitting your opponent either through minions or not. this will increase your lane time dramatically and reduce theirs.
defending:
In short against cait's piltover your best bet is to never stay still and always keep a random dodge pattern, this will insure much fewer piltovers hit you. if you stop for half a second for a minion kill make sure your moving immediately after your attack animation.


yordle traps:
Attacker: what a powerful ability this is when used right! and useless when used wrong! so each way to use it is explained

Harassment traps:Use them this way when their is no enemy jungler to worry about and your confident of your team calling MIA's or your own map awareness. in essence you will be placing traps closer and closer(then directly at) their tower so that they have less room/places to dodge too. this makes hitting with piltover much easier, and makes it much harder for them to properly last hit minions, a win win situation.

Defensive traps: place these in bushes to give you sight on enemy's entering them even if they dont get close enough to trigger the trap you can most of the time still see them entering and get away from a potential gank. this is a MUST if they have a jungler or your team isnt calling MIA's.

Defending against traps: NEVER purposefully step on traps when coming back from base/death just because you have full health and can "afford" it. you cant, stepping on 2 or 3 traps before Cait gets back in lane/can get to you just means that your already missing 1/4 of your life and she can push you around that much easier.
DO step on traps when you are low health and KNOW she can not hit you with anything before you go back to base, this makes it a waste of mana/harassment on her part. And ALWAYS be careful of entering bush's around Cait. Even if you dont step on a trap if you are close enough to it she WILL see you.

90 Caliber Net:
Attacker: this is NOT an offensive skill, its a defensive skill that acts like a flash and exhaust all rolled into one. save mana for it ALWAYS and make sure its not on CD! this will save your life more than you know!

Defender: Never chase Cait in a straight line always try to zig-zag so that her net misses you and you can land that killing blow

ULT:
Attacker:
By the time you hit level 6 unless they have already based they should be low enough health to ult for a finish, if not and you have gold to buy a piece of gear go ahead and lead with it just as some extra damage, base come back and continue harassing(but not so much your force them to pill before ult is up, this can easily get your first kill if you havent killed them already). This ult SHOULD be spammed, dont save it just for when they are low health for a kill, use it to get them to mid health or to make them critical health so that they have to B, this is where you really start getting your lanes towers down.

Defender:
Unfortunately you cant avoid it(unless a teammate steps into its line of fire, or she is CC'ed). If your Cait is doing this properly you really have no defense against the harassment ability of this ult. Basically: tough it out.

Using Cait's spells:
More of this is covered in my game explanation, and to reiterate these spells are only worth while IF you use them as described, otherwise other spells can get you much more use.

Tele: lets you get back to lane with minimal time/xp/gold lost for a base heal/item
Ghost: great for escaping mid-late game, but i generally use this early game(while tele on cd) to get back to my lane faster, since my second base i generally have zerker boots this gets me back very fast with less time/xp/gold lost for a base.

Now that you know how to use her abilities and what to watch for, lets get to her lane game.

Ok here is where i really get into what my play style is, this will be the lengthy section so please bare with me on this, it will take a while.

Ok to start with we grab dorans blade and head to your lane:

MID LANE

Wraith Camp(if you have no jungler): This is how you get a exp boost that will greatly help your early game harassment.
use piltover on the lesser wraiths and kill 2 of them, then run to lane. Why only 2? any more and you not only loose to much health but you also miss out on the first minion's dieing/last hit, so only do 1 or 2 of the lesser wraiths then book it.(do not ghost, if your new to caitlyn do not use this trick, the missing health will get you killed/pushed around too much)

Mid Harassment: remember those wraiths? congratulations first wave down, your level 2! yes already a level up on our enemy that means that most of the health you lost to the wraiths is back just in natural level HP! AND YOU HIT HARDER! This of course is very important, any leg up early game gives you a HUGE advantage. Continue to piltover and trap your enemy until he is either dead or forced to take the magic blue pill. At this point you should/will be low mana and hurt some, stay to get some tower damage in(1 wave max 2) then base and buy your first item(or 2 if you got a kill). i recommend the dagger first over boots(unless u have enough for boots+dagger or just zerk boots already) why dagger over boots? because your going to tele back to lane, total time out of lane 10 seconds, your opponent should be out of lane a full minute. Yes you robbed him of another minutes worth of xp, while loosing almost none yourself! This means that you should still be at least 1 level if not 2 levels up on him which gives you a huge damage and life advantage over your opponent, meaning your harassment is in overdrive now. Continue to harass/kill your opponent till you have first tower down, this (for me or any other good Cait player) will happen around the 8-12 minute mark, congrats you just got your team 150 global gold! Base and get another item or two after boots i HIGHLY recommend getting another dagger for cleaver and not saving for BF, get BF after dagger the AS boost is worth it for tower damage/harassment.

Tower down Mid lane:Now here is where the real fun begins
your options are wide open now you can:
1. keep pushing mid if the enemy team isnt ganking you much/at all, somehow this still happens even in mid ranked elo last 3 games as Cait ive had both mid towers down before 15 minutes(last game was 13:56 2 towers down mid).
2. Push back your opponent some then start ganking other lanes yourself to help get their towers down, the great thing about cait is she can harass low health players at tower that forces them away from it or to base so you can get other lanes more open very fast.

Mid-late game:
Now here is where cait starts loosing her early game dominance and starts playing the roll of support damage, and where the rest of my build gets explained.

Why not life steal/crit early game, why so little until late game? Your support you should be doing Piltover and Ult as your main forms of team battle damage, both of which get massive improvement off of your ad and none from crit/AS. Which means its basically useless to a harassment Caitlyn. As far as life steal goes you CAN and i do get vampire after cleaver so that i can take minions/buffs easier and for longer but before then you will be basing so often that it will provide very little benefit to you and lower your damage output in the mean time. Also the other major benefit to doing Caitlyn this way is she becomes your main damage output on turrets letting you get them down insanely fast.

As far as playing mid-late game goes its really rather simple in idea harder in practice: stick with the team do damage from the back you are not a solo champ you see someone at full health you run(unless you ABSOLUTELY know you arnt being baited/you can take them). You are squishy and you dont have the time needed to put out damage without someone to take the attention off of you. This really can be the hardest part about playing cait, especially with my build, to go from a lane pushing turret destroying monster too a meek mouse taking pot shots at the cat.

That is the basic mid-late game for Cait, played correctly you will be tower killing and killing champs at tower with ease.

SIDE LANE
First Skill: pitlover OR yordle, both have great power for side lane, you can trap/stun them in bushes for a easy kill OR do damage to both of them with piltover. really up to your play style(i still piltover personally)

First contact:
Ok here we dont have the power/health to be taking on any jungle minions for an exp boost so push your bushes with a teammate as fast as possible. if your teammate has exhaust have him exhaust the squishiest character and concentrate him for first blood. Its ALWAYS a good idea to check their side of the bushes with either a trap OR piltover so that you get some damage in on them if they are their.

After first contact:
Here your basically playing the same game as before, but your going to want to be more conservative with Q, trying to line up both champs(or just using on the lowest health one). try to get them both very low/dead so that they are forced to base and you can take at least half damage to their tower.

Tower down/laning phase ended(whichever comes first):
for the former let your lane partner handle your lane solo for a few and go help mid or the other side lane get a tower or two down basically you should be all over the map at this point in all lanes and no lanes, harassing as much as possible.

Group Phase: play it like you played for mid

SOLO TOP

Depending on your skill level (and that of your opponents)this is either a horrible idea or a great one, by that i mean you can still harass from your turret very well for a short period of time, but because of your low mana pool and squishy character you will tend to have to base far to much over other tankier/healing characters. about the only advice to give here is to never ever ever ever leave your tower to push a lane, you are ganked far to easy being by yourself.

Why Piltover over Yordle?
Quite simply yordle doesnt allow for the level one domination in lane needed for my play style and build. As well if your playing mid and getting some wraith action yordle does not help their but piltover does.

Why not XXX item?
For the first 3 pieces of gear i think the explanation ive offered so far is rather sufficient if not i will update in the future, for the final 3 end game items these change often depending on what my team needs/what the enemy team is doing, they are by no means set in stone, change it up, get back to me on what you find, maybe i need to change MY main end game build. thats why this is a guide :)

Note here: the reason why i say those first 3 items for cait is ive tried just about any other combination of items you can think of and none of them give her the early game harassment those 3 do, i mean its not even close going with say IE instead of Cleaver. play my way, then try your other item, you will see. The armor pen +attack speed make a huge difference.

Why am i making this guide?
Partially i was bored, but mainly because i didnt/havent found another guide like it specifically for my play style but as well that trys to give new players on both sides of the equation an idea of how cait operates her abilities. That and im always looking to improve myself/this guide so i want the feed back a large community like MOBAfire can give me.