Caitlyn is an excellent champion. Many criticize her for her lack of unreliable CC, but her ridiculous damage, along with a unique ultimate, makes her a viable carry for any game, even ranked games. In this guide, I explain in depth how I play Caitlyn. I hope you find it usefull.

PROS

Great damage output
Superior map control with Yordle Snap Traps
Easy escape with 90 Caliber Net
Amazing ultimate for finishing champions
Farming Skills and Lane Superiority
Her Resistance skin is awesome

CONS

Very squishy
Focused in team fights
No crowd control skills
Weak against heavy crowd control
Red buff dependent

Caitlyn uses standard dps runes, specialized in armor penetration, mana regeneration and magic resist.
Greater Marks of Desolation Greater Mark of Desolation provide enough armor penetration for your attacks not to be tanked so easily.

Greater Seals of Clarity enable you to constantly use your skills, and have a consistent source of mana.

Greater Glyph of Warding is pretty self explanatory. Every character needs magic resist in today's metagame.

For Quints, i usually run one Greater Quintessence of Desolation Greater Quintessence of Desolation and two Greater Quintessences of Fortitude to give Caitlyn extra armor penetration and survivability, but 3 Greater Quintessences of Desolation Greater Quintessence of Desolation should work fine.

For masteries I recommend 21 in offense, 0 in defense and the remaining 9 points in utility. If you took Ghost and Exhaust, remember to take the improved spell masteries.

Start off with a Doran's Blade . The reason Doran's Blade is a great item is because it gives damage, HP and life steal which is great for early survivability. On your first trip back, get Berserker's Greaves . This shall grant you a little extra attack speed, which is always good. Mercury's Treads is also an option if there is too much CC on the other team. Next, proceed to buy Infinity Edge , starting with B.F. Sword . You might ask yourself why Infinity Edge so early, the answer is your early game damage will come from Piltover Peacemaker and Ace in the Hole , so the enormous AD from Infinity Edge scales with both skills to give them insane damage. After that, start building Phantom Dancer , making sure to buy Zeal first. At this point, your basic attacks should be doing insane damage. Nevertheless, you are in trouble if the enemy team starts building armor. Thats why I recommend Last Whisper as your next item, to make sure your attacks penetrate the opponents' armor. Next, you need to get The Bloodthirster . This is an amazing item on Caitlyn, and any Ranged dps. Make sure to kill a lot of minions, to max the stacks on your Bloodthirster . Finally, you need to examine the game. If you are getting focused (which is likely) and life steal is not enough to keep you alive, proceed to buy Banshee's Veil . If they are not able to kill you, and feel confident about yourself, get Madred's Bloodrazor to pull out even more damage, specially to tanks. Remember, never give up defense for offense; if you are getting killed often, you will keep loosing your Bloodthirster 's stacks, which will make your build less effective.

At the beginning, learn Piltover Peacemaker . That will be your main source of damage early game, when your basic attack isn't strong enough. Remember Piltover Peacemaker gets weaker the more targets it passes through, so keep aiming at enemy champions directly, and not through minions.

Second, learn 90 Caliber Net . Although not viable as a slow, 90 Caliber Net is absolutely amazing when it comes to saving you from danger. When you're being followed, aim 90 Caliber Net at your follower. Not only will it slow the target, it will also push you back and get you out of his grasp. Be cautious about Olaf's Ragnarok and Yi's Highlander , because you won't be able to slow them when they're active.

After learning another point in Piltover Peacemaker , learn Yordle Snap Trap . DO NOT underestimate your traps, they can turn around a fight when used wisely. Remember to place your traps in bushes, preferable at the edge of bushes were enemies can land without noticing. Also, place traps in the sides of the lane, especially if the enemy team has a jungler. One of the most important uses of your traps is to put them behind the enemies, that way, you will get them as they try to escape. Finally, remember to use Piltover Peacemaker in combination with Yordle Snap Trap , aiming a clear shot every time an opponent steps on the trap. After maxing Piltover Peacemaker , proceed to max Yordle Snap Traps , leaving 90 Caliber Net for last.

At levels 6, 11 and 16, you can learn your ultimate, Ace in the Hole . This is one great skill, and is what makes Caitlyn a fun and powerful champion. I've seen many Caitlyns initiate with Ace in the Hole to start the fight with damage in their favor. Although this may prove useful sometimes, I've found the best use for Ace in the Hole is for finishing off enemies as they escape. Its ridiculous range, along with high base damage and nice AD scaling makes it a wonderful tool for getting kills early and late game. However, there are some important things to keep in mind while using Ace in the Hole . First, make sure you will get the kill. There's nothing more annoying than wasting your ultimate and watching your opponent escape with little HP. Check the base damage of your skill at levels 6, 11 and 16. Also check the remaining HP of your target to make sure you can land a kill. (Note that armor reduces the damage of Ace in the Hole ). Also, you must make sure there are no opponents blocking the shot, or in position to block it. If you are going to take the shot with an enemy nearby, make sure he's far enough not to block the shot.
When using Ace in the Hole , also consider what champion you're aiming at. Some champions, like Zilean and Dr. Mundo can survive Ace in the Hole easily.

Caitlyn works well with any combination of , but I recommend getting one escape spell ( or ) and one offensive spell ( or ).
is very good for 1v1 performance and can almost ensure first blood if played smart. I recommend it ONLY WHEN you are very comfortable playing as Caitlyn, have acute map awareness and are playing in a pre-made team with lots of cc.
On the other hand, ensures survivability, but lacks the offensive gameplay Caitlyn needs. It is only recommended if you are new to Caitlyn, and are not used to escaping with .
I personally go with Ghost because you will constantly chase/be chased by enemies, and it provides a safe escape when used with 90 Caliber Net . Ghost is also useful when chasing an enemy you want to Ace in the Hole . 90 Caliber Net can be used to go through walls and structures, so it can replace Flash in that sense. I prefer Exhaust over Ignite , because it can also be used as escape in 1v1 situations and proves awesome if you have the mastery.

As Caitlyn , you can either take mid, side lane, and even solo top (when your team has a jungler). If you take top or bot, you can use the bushes to increase the effectiveness of your passive, Headshot . If you take mid, you get the 1v1 superiority, along with a better chance to Ace in the Hole your target without interference. Farming is easy with Caitlyn. Her base attack makes you last hit minions without much difficulty, and the Headshot bonus serves well to this purpose. Your range should enable you to dominate any lane, and easily deny enemy champions. In my experience, only few champions can outperform Caitlyn at mid. Vladimir's can mess up your Piltover Peacemaker 's harassing, and Tristana's range can be a challenge. If you are being dominated, feel free to tower hug and wait for late game, where you really start to shine.
During laning phase, keep using Piltover Peacemaker against minion waves and to harass champions. Use it enough to keep your enemies bruised, but don't abuse and run out of mana.
Always have your Yordle Snap Traps in place. The reason I insist on placing traps is because their use may seem futile, but you will be surprised about how often people get trapped with them.
Keep in mind to always get . As soon as laning phase is over, start killing Lizard Elder, or asking your jungler to leave you the buff. Steal it from your enemies' jungle once you consider it prudent. You NEED to have Red Buff most of the time. It gives your opponents practically no chance of survival, especially late game.
Remember your role during team fights. You are not a tank, do not jump in the middle of the action. Always stay at a safe distance; you can't afford to get catched by Amumu's or Kennen's . Come when the team fight has initiated, always keeping your distance. Shoot your Piltover Peacemaker when enemy champions are lined up, and finish them off with your empowered basic attacks.
When you are getting a monstrous amount of kills, it is likely that enemies will start focusing you. If your team is good, they will be aware that Caitlyn is a squishy champion, and will protect you. Always play defensive, however, keeping Ghost and 90 Caliber Net ready to escape.