(Passive) Headshot: Headshot
INNATE: Caitlyn's next basic attack against enemies Root icon rooted by Yordle Snap Trap.png Yordle Snap Trap or Slow icon slowed by 90 Caliber Net.png 90 Caliber Net gains 650 bonus range and deals 50% (+ 0.5 × total critical strike damage modifier × critical strike chance) AD bonus physical damage, modified to 150% AD versus non-champions. Additionally, Caitlyn gains 10% bonus attack speed and her regular basic attacks each generate a stack of Headshot, doubled when attacking from brush, granting her next basic attack the same bonus physical damage at 6 stacks, though this does not benefit from bonus range nor is it consumed on other instances of Headshot.

(Q) Piltover Peacemaker: RANGE: 1250 COST: 50 / 60 / 70 / 80 / 90 MANA | COOLDOWN: 10 / 9 / 8 / 7 / 6 | ACTIVE: After 1 second, Caitlyn fires a projectile in the target direction that deals physical damage to the first enemy it passes through, after which it expands in width but deals only 67% damage to all enemies it passes through thereafter. Enemies Sight icon revealed by Yordle Snap Trap.png Yordle Snap Trap always take full damage from Piltover Peacemaker. PHYSICAL DAMAGE: 30 / 70 / 110 / 150 / 190 (+ 130 / 140 / 150 / 160 / 170% AD)

(W) Yordle Snap Trap: RANGE: 800 / 67.5 | COST: 20 MANA | RECHARGE TIME: 45 / 32.5 / 20 / 12.5 / 10 | HEADSHOT DAMAGE INCREASE: 30 / 70 / 110 / 150 / 190 (+ 70% AD) PASSIVE: Caitlyn periodically stores a charge of Yordle Snap Trap, up to a maximum amount stored at once. ACTIVE: Caitlyn sets a trap at the target location that arms after 1.1 seconds and lasts up to 90. After the maximum amount of traps is laid down, deploying another immediately destroys the oldest one. Enemy champions who step on a trap set it off, Root icon rooting them for 2 seconds, during which they take increased damage from Headshot.png Headshot, grant True Sight icon true sight of themselves for 9 seconds, and become immune to Yordle Snap Traps for 4 seconds while they remain in the area.

(E) 90 Caliber Net:RANGE: 950 / 400 | COST: 75 MANA | COOLDOWN: 16 / 14.5 / 13 / 11.5 / 10 | MAGIC DAMAGE: 70 / 110 / 150 / 190 / 230 (+ 80% AP)

ACTIVE: Caitlyn fires a net and dashes in the opposite direction, dealing magic damage to the first enemy hit and Slow icon slowing them by 50% for 1 second.

(R) Ace in the Hole: RANGE: 2000 / 2500 / 3000 | SPEED: 3200 | COST: 100 MANA | COOLDOWN: 90 / 75 / 60 PHYSICAL DAMAGE: 250 / 475 / 700 (+ 200% bonus AD) ACTIVE: After a brief delay, Caitlyn locks onto a target enemy champion and channels for 1 second. At start of the cast, Caitlyn gains True Sight icon true sight of the target.If Caitlyn completes the channel, she fires a homing projectile toward the target that deals physical damage to the first enemy champion it hits. Other enemy champions can intercept the shot.

Ability Details from: http://leagueoflegends.wikia.com/wiki/Caitlyn

This is a big part of Caitlyn's damage in general. If you have a support with CC (Ex. Karma / Morgona) As soon as they are CC'ed throw a trap under them. As soon as they are out of the initial CC they will be rooted by your trap. From here AA to proc your passive and use your Q, which will always do 100% to targets that are rooted from traps. If there is no CC you will have to predict where people will be in 1.1 Seconds, for you trap to proc, from here do the listed combo.

The best way to get away from someone is to: E Them and flash away, they are slowed and you are a far distance from them.
E them and if they are still pursuing you (This can be difficult) predict their movement and place a trap where you think they will be in 1.1 Seconds, once they are rooted you can try to turn the fight around or run away.

Try to roam with a headshot, this will give you the highest burst. The best combination you can do 3 Headshots simultaneously. Your E and W have to hit to do this. (Get them into a trap) > AA > Q > E > AA > AA > (R if possible)

Caitlyn is very good in lane. Push them under turrent and deny them CS by placing traps in front of them so that they cannot farm efficiently. Try to trade with your Headshots / Q.