i will explain all of this better in this guide but just wanna get your attention with the small good facts :)

I have called the guide for sniper mentality because of 1 reason... that is the mentality i have when i play cait.. and its what ill tell you a bit about.

normally in cait guides ppl say get exaust and ghost so you can get away if ppl try and gank you...dont listen to them... just be a real sniper. stay in the back, get your weapon ready and shot the targets your team needs to have killed fast.
2 things i like is not using the summoner abilitys that saves me if i mess up.. but instead use abilitys that prevents me from messing up.. i use Clairvoyance for scouting, scout for your team, scout before you step out from the bush or from the tower. scout for a gank..

And Rally.. i use it for team fights.. and when that akali is running away from me when i get her semi-low.. i pop rally and use ulti on her :) BOOM HEADSHOT!

well i hope you wanna read more. and comment the guide. ty for reading it :)

PLEASE only comment if you have tried it out.. dont just call me things.
only trying to help others.

Rally:
The only ability in the game that boosts dmg... think of it like this.. someone is running away from a 5on5 teamfight.. and your ulti would make around 600dmg on her.. and she got 625hp... pop rally and BOOM she is dead :)
Team fights... being avg on both teams in teamfights?, not with rally on your team :D
..first blood too.. standing in your bush when 2 fools run towards you and you just pop rally then the chance for getting First blood good.

Clairvoyance:
the best scout tool in the game.. stop using cash on wards.. this ability gives you all you need for playing caitlyn... if you cant target someone running away from you with your ulti use this ability and you can get him locked with ulti :)
use it so you dont have to use exaust or ghost. by that i mean.. check that bush if you think a gank is inc. help your teammates so they wont get ganked.. or help your teammate making a gank on enemy junglers.. alot of players have a hard time jungleing if they lose blue or red buff, gank them so they get behind in exp.

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Other spells that i find okay for caitlyn is:
Exhaust this is great for ppl running to slow them.. or for that towerdiving trynda :)
Flash i know this spell is OP and i wish riot would delete it.. but to be honoest.. i hate it i fail with it all the time and your range on cait is so long i dont think its that useful.
Ghost good to counter ppl having ghost running from you or trying to gank you while they use ghost.. or getting faster into battlefield :)

Some ppl maybe find this spell useful but i dont like it:
Clarity is okay.. but again.. with my build this is overdoing it.. but if you went for stacker item and manaregen runes this could be okay.
Ignite to low range on this..but for that firstblood or that Overfeeded mundo this can be helpful :)
Smite I have not tried to jungle on cait yet. but i will come back to you when i have used more time on this ""there will be a whole chapter on it when i have used more time on it""
Teleport before i used clairvoyance i used this one.. i love this spell being everywhere on the field is my play style :)

Spells i think is stupid to take on caitlyn:
Cleanse ? are you joking.. if you use this on cait.. pick another champ :P
Fortify ask your tank to get this and make him use 1 mastery point on it so it does splash
Heal is worthless. have 1 healing pot you on if your against a karthus, alot of others takes this and that is good.. so if you need the healing from this akility its in a teamfight where your friend has the spell for you :)
Revive ? if you fail that much you think this is okay then play a tank :) or another game hehe.

Red: Greater Mark of Desolation - THIS IS A MUST HAVE armor-pen is the best rune stat for caitlyn.

Yellow: Greater Seal of Attack Damage - i prefer having dmg runes in both yellow and blue so that i dont fall behind on dmg when going for manamune.

if you like to you can go mana regen on the yellow runes they are called Greater Seal of Replenishment making it posible to go for the stacker item instead of manamune. what ever you prefer :) i prefer manamune.. making me stay longer on the battlefield.

Blue: the same as the yellow runes.. Greater Glyph of Attack Damage dmg runes.. if you like this is also the runes you can change to mana regen. Greater Glyph of Replenishment

Quin: Greater Quintessence of Desolation - THIS IS A MUST HAVE armor-pen is stil the best rune stat for caitlyn.
squishy champs becoming even more squishy and those tanks will before easier to harras.

My item list aka build is cheap to start with but late game its expensive.

Doran's Blade
is great early game.. tho you feel like you miss mana :)

the next item i build for is:

Ionian Boots of Lucidity
the reason i take these shoes instead of attackspeed is the cooldown helps on ulti and my whole build is not build around the headshot ability.. its build around Q and Ulti :) standin in bushes is still Very important..

Manamune
while building this its important to go for manaregen or the longsword. it makes you stay longer in the lane and make more dmg.

and this is the CORE or my core build.. i got 2 items more in my "core" build but i cant cant cant live without these 3 items.

Hexdrinker
this is the BEST item ever made.. thank you riot.. a dmg item with great survivability, when that karthus pops ulti and you survive on this item.. 70% or more of all champs have some magical attack and this will save you.. and best of all. garens ulti is magical :P

The Brutalizer
if you get this item cooldown reduction is on 28%
15% from shoes.
10% from this item
and 3% from masteries.

This is now the Core core core build.. now you got all the dmg you need for normal fights and you got survivability and you got alot of cooldown reduction and ofc the mana needed for anything. now you can build for the fights...

if you just wanna do more dmg i prefer doing like i do mostly:

Bloodthirster
and then if you get cash enough sell your dorans and buy 1 more

Bloodthirster
the reason i take this item instead of infinity edge is the stacking Attack dmg.
this way i play caitlyn is all about the dmg :)

21-09-00

its the way i like to play it.. i have thought more and more about this and tried alot of different combos.. but it seems to be the only way to go.. ofc alot of ppl guides to go for 21-00-09 for the extra mana and some goes for the extra exp. but in the big big team fights i feel this gives me more.. tho after placing the 21 in offensive i think you should place the last 9 as you please :) some would even like placing 2 in the extra dmg to minions to be sure to get more minion kills..

Early Game:
This is the part that matters the most in my playstyle. if i get just 1 or even 2 kills before 5mins have passed without dieng then i will be in such an advantage that i do extreme dmg even on tanks. or ofc 1 tower at the 5-6mins timer. mostly i play with a dmg dealer.. so together we nuke us the way to FB and getting 2nd target to 1bar and then they run home.
( Rally is the thing that makes us kill 2nd target)
only reason some still survives is flash. that **** spell makes ppl get away in all kinds of situations.

when minions are appearing i stay in bush so i always get more dmg output and always stay in line for your Q to be hitting either enemy champs or farming minions. other then that i use alot of time scouting with clairvoyance and just checking out my enemys playstyle before we will get to mid game harras with right click and Piltover Peacemaker and get the kill with a saved Headshot or a skilled Piltover Peacemaker shot :)

Mid Game:
this is where you have to check out the minimap at all times and be the helper for all your mates. if someone is getting pushed or are pushing help them.. make sure that enemy dosent get away. but ofc dont be alone anywhere at anytime.

Late Game:
now you should have enough kills or assists.. and your items should make you hit harder then a truck.. go find squishy ppl and beat them hard. use a teammate as bait and nuke the enemys from the bushs. be all your teammates need you to be :)

and yes.. if your team fails there is nothing you can do with this build :) if you dont know how to get alot of kills and feed your self.

Pros:
*Insane range
*INSANE DMG!
*Really good teammate.
*Killing machine of runners.. the ulti makes sure no one gets away. :)
*Insane early game, and great in late game if you have a good item build.
*An amazing tower pusher and farmer.
*Great escape mechanic.
*Caitlyn is a sniper and i just love snipers.

Cons:
*Hard to do dmg if behind in exps
*Only 1 dmg spell and if you dont know how to use it caitlyn is hard to play
*Really really squishy even in late game that is why i use the clairvoyance for scouting.
*Recommended? Riot?? is this for real??
*Caitlyns Traps is way to visible.