Caitlyn is an extremely powerful AD Carry. She has a longer range than Ashe, stronger abilities, and is more useful overall as a damage dealer. However, she doesn't have the ability to kite quite like Ashe does, nor is she able to reliably stun her opponents. That being said, Cait is nonetheless one of the most useful carries in the game.

Pros:
Ridiculous range
High damage output
Fantastic ult for sniping running champions
Stun and a slow
Can easily escape jungle ganks, as well as most mid ganks
Good poke
REGULARLY deals the most damage in games
GREAT farm capabilities


Cons:
Squishy
Enemies will try to focus you (doesn't work if you fed early)
Kinda slow without a phantom dancer
Suishy =(
Ult can be a little bit tricky to land, but most people don't think quickly enough to jump in front of it intentionally.
Needs a BF sword early to be effective
Squishy D=

For Caitlyn I typically run Armor Pen marks and quints. With 25 armor penetration at lvl 1, your attacks essentially deal true damage to your lane counterpart. For levels 1-5, this is incredibly useful for both her poke (Piltover Peacemaker) and her passive (Headshot).

For seals I take flat attack speed. Without these, Caitlyn attacks way too slow to effectively farm/harass in lane before she gets any attack speed buffs. The difference is definitely noticeable.

For Glyphs I run CDR/level. Mana regen glyphs would be helpful as well, but I enjoy the reduced cooldown on Cait's ult (not to mention her 50 cal net) too much, and would rather just take blue if I need mana.

Masteries are pretty straightforward. 21-0-9, with a point in Teleport instead of Ghost. Personally, I don't like running Ghost, but I will explain that later. Be sure to pick up the extra experience in the Utility tree, because it gives you a definite hand up on getting your Ult, which is what it's all about.

Now, you might be wondering why the Negatron cloak is just sitting at the back of the build. That's because I only buy that as a judgment call. If my opponent is AP, I will buy it around the time I buy my BF sword (BF sword comes first if I have 1700 gold, but less than that I buy Negatron cloak first). It really ruins your opponent's chances of killing you.

The first time I go back, unless I've died/almost died, I have no less than 1000 gold. This allows me to buy a Vamp scepter and basic boots. Your damage doesn't go up, but your ability to stay alive/recuperate after getting hurt is tenfold better. It'll allow you to farm faster and reach that BF sword super quickly. I prefer going back with around 1500 gold, because then I can come back with boots and the vamp scepter.

After you get your bloodthirster, you have to start questioning the other team.
Are they pure AP? If so, buy Negatron Cloak early. This also applies if they have a AP Carry that is feeding on your team, and if you're laning against a (good) AP carry.
Are they pure AD? If so, hide behind your tanks.
Are they super tanky? If so, maybe buy a Madred's or a Black Cleaver before your I.Edge.

No build is ever perfect. Each game, requirements will change. What worked like a charm one game might not work so nicely the next.

Piltover Peacemaker is your true damage dealer early game, so take that first.

50 Caliber Net is also a very important escaping tool. It shoots you backwards (opposite the direction you shot) AND it slows the person chasing you (if you hit him/her), which boosts your chance of survival immensely. It also shoots you through small walls, so be sure to use that to your advantage when escaping ganks.

Yordel Snap Trap... well this one is hard to explain. It's pretty lame in that it doesn't give you vision when laid (like Teemo's shrooms), doesn't deal significant damage (not early enough, at least), and is easily avoidable because of it's bright, flashing color. HOWEVER, this skill has gotten me more kills than I can count early game. I get this skill at level 4 primarily because Piltover's damage and 50 cal's escaping are more important to me. Sometimes, depending how my lane looks, I will switch Yordel and 50 cal, but that's just a judgment call.

Piltover Peacemaker is Cait's best damage dealer early in the game. It's a skill shot with decent range and passes through units (dealing reduced damage each hit). Now, that doesn't mean spam it like crazy. If you do that, you'll be out of mana and your opponent in lane will eat you alive. Use it once per wave or so, hitting as many minions as you can in the process, while always aiming for the enemy champion. The point early on is to keep your opponent from getting farm, and to scare them out of range of minion experience. Do this properly and you will typically kill your opponent first.

Once you reach level 4, start laying traps. Some good formations to keep in mind: Lines and triangles. Keep the lines fairly evenly spaced across your lane, with the middle trap slight ahead or behind the others. The enemy champion will be too worried about hitting a trap to chase you beyond that line, but if they do manage to sneak through the tiny spaces, hit them with your net and run. The traps will pick champions who use a skill through it, like Akali's Ult, which gives you a little extra time to run away in that situation. Use a line when a lane is pushed hard in either direction.
The Triangle setup is used when the lane is pretty evenly matched. Keep them fairly spaced out in the middle of the lane. It just gives the enemy something to be cautious of, which takes a little of their concentration away from killing you/farming effectively. And, of course, when they hit one of your traps (which they will inevitably do), hit them with Piltover.

Always keep your cooldown for 50 Cal Net up. Do NOT use it as a damage dealer, because that is it's worst quality. If this skill did NOT do damage, I would use it and love it just as much as I currently do. This skill is used to escape ganks, run from your opponent, and to hop through walls (escaping, taking shortcuts, juking, etc). It also has an alternative, slightly less common use: chasing. I played a game recently against a Corki in mid, and my first two kills came from closing the gap with 50 Cal Net and hitting him with my Headshot. This use is harder to judge because there is a brief delay to use the skill, as well as a brief delay AFTER you've used the skill, which makes judging the distance difficult. I hardly ever use it for this purpose.


Cait's passive demands that you auto attack frequently. Levels 1-6 (or before I get my BF Sword), I hit each minion once or twice before last-hitting them so that I can get my Headshot ready more frequently. This does significant damage to your opponent at these early levels (especially if you crit them!) and is a perfect harassing tool. It is also great for farming, and is particularly useful for last-hitting the canon minion. Doing this also allows you to push your lane a lot faster than your opponent, keeping them on their heels and unsure of what's going to happen. It pushes them into their turret, and they lose farm. Stay in lane and continue doing this until one of the following three events occurs:
You Die. However, if you're doing everything right, this won't happen unless your opponent is incredibly good, or their jungle ganked you very well.
They Die. Kill the wave and B, but only if you have more than 1000 gold.
You ALMOST Die. This will happen. It always happens. If you get too low on health, camp the turret for a little bit if you need to get minion xp, then B.
Teleport back to mid, and <10 seconds after you B you will be at full health in your lane again. THAT is why I take teleport.

Quick notes on your ultimate: When you first get it, you will deal approximately 220 damage (WITH COMPLETE RUNEPAGE). Except against Rammus. Don't use your ult on Rammus, it's a waste of time ahahaha.
That means whenever your opponent has less than 2 full health bar ticks, you can probably kill him with your ult. Abuse this knowledge.

Though people are going to disagree with me, I much prefer to take Teleport and Flash. Caitlyn is pretty slow, but has a number of escape options. Ghost doesn't augment her all that much, and if you're in a situation where you need to ghost, you're dead already anyway. You should never get into a situation where you need to ghost, because she can so easily jump through walls.

I take Teleport because it enhances my lane presence, and it is completely under-appreciated.

Flash should be obvious.

Just some proof of concept here. That's really all that is missing.

Remember, take advantage of harassing with your Headshot, be conscious of your mana usage (Cait eats through it like Kobayashi does hotdogs), and abuse your ultimate!