I started to play her when she was free. I always played with mages and some ranged, but i never founded one I really loved. When I tried her, I immediately understand the way to play her. Damage, critical strike, attack speed and a bit of lifesteal makes it a perfect ranged killer. She's easy to play, for me so I guess for you too, and I hope you will enjoy her as I do.

Caytlin is a perfect farmer, killer and ranged. Her abilities are powerful. She doesn't need a lot of mana, because of her low mana eater abilities and her empowered armor that increased at each level. Her passive makes her a great damage dealer and a great farmer. She's a sniper character, so she has a long range and she deals a lot of AD damage.

1- Piltover Peacemaker:
It is a powerful skill, that is combined to your attack damage. Its easy to farm with this skill and to get a long distance kill. It has a short cooldown and a low need in mana. But warning: the amount of damage is reduce by the amount of peoples it touch. Also, pay attention to the ranged of the skill.

2- Yordle Snap Trap:
A good trap that immobilizes, makes a good amount of damage and reveal the champion. Also, it doesn't need a long time for the cooldowns and the amount of mana needed is low. Another thing is that the traps are visible to enemies, so hide them in the brushes.

3- 90 Caliber Net:
Not the best skill of Caytlin, but useful. It shoots a net that slows the enemy and deal damages. The great thing is that Caytlin, after the shot, knocks back, making it a good skill when you need to pull back. But because this skill use the ability power, and that Caytlin don't realy use AP items, it must no be the principal skill of the build.

4- Ace in the Hole (ultimate):
The sniping skill. A lot of damage, for a low mana, and a big range (2200 at level 18). When an enemy is pulling back, you spot him and shoot him. It is great against low healt enemies, but if a support is with him, its frustrating. A big problem with this skill is that if someone get in the road of the bullet, he received the damage, making you fail your kill.

5- Headshot (passive):
What a great passive. After 7 shots, your next shot deals 150% of your damage to champions, and 250% to the minions. Also, in the brush, the shots count as two. So, you need to provide her a lot of attack damage items, to get this skill more effective.

-First, you need to buy a Vampiric Scepter, so you can farm almost indefinitely. With her big damage amount and her passive, she can gain healt rapidly.

-After, buy the Berseker's Greaves. Now, you will gain a lot of attack speed and movement speed, just what you need at this point.

-We continue with Bloodthirster, that provides attack damage, lifesteal and a great passive that makes you gain lifesteal and AD for each kill you make, even minions.

-*The 3 first items are needed at the beginning, but after, the order may changed for you.*

-The be more OP, grab a Phantom Dancer to gain great amount of Attack speed, critical strike chance and mouvement speed to chase down enemies.

-If you want to have greater critical strikes, thake the powerful Infinity Edge, that gives tones of AD and better amount of damages for critical strikes.AMAZING!!! :D

-Also, you must buy Last Whisper to get more attack damage and armor penetration, to completly pass thrue the enemies armor.

-For the last object, choose amongst Frozen Mallet, Ionic Spark or any surviability items. Good ones can be Wit's End, Banshee's Veil or any kind of armor, dependly of the games situations.

Runes... great when you are... level 20. Don't buy them before, because they are better at level 20, with the Tier 3 unlocked. I made this mistake, so that's why I'm telling it to you.
So, to have a great rune page, you will need:

-Armor penetration
-Mana regeneration
-Magic Resistance

1-Desolation Marks and Quintessences:
The attack damage of cayltin is a need for her: Her skills are better for each attack damage she has, and her passive makes more damage too. The armor penetration is perfect for Caytlin, and not frequent with the items (only 4 items provide it). So, we need to use some runes to increased the amount armor penetration. The attacks will do more damage, by passing true the enemy armor. This is awesome against enemies (junglers, tanks and some support) that have a lot of armor. It has a lot of utilities to Caytlin. That's a keeper. :P

2-Shielding Glyphs: Mayby ain't she a tank, but she's still squishy and vulnerable. Her health is regenerating through lifesteal and armor is already gain each level. What's missing? MR!!! Grabing theise runes will bring her enough protection to survive team fights and mage ganks. A good choice, indeed. ^^

3-Clarity Seals:
Because she has not a lot of mana and that she might needs some for her great skills, we need some mana regeneration. She don't need a lot, and a bit more then the normal amount can make her better for killing.

I did go with a 27-0-3, because she's first of all an AD champion. I take:
- Ignite boost (to kill even more ^^)
-AD and AD/lvl
-Attack speed
-Armor penetration (just what we need :D)and Armor penetration % (just like Last Whisper)
-Lifesteal (not enough to survive long, but at the begining it's good)
-Critical Strike Damage (to boost Infinity Edge)

She doesn't need defense, because she's range and already has good armor. I choose at last utility, for better Flash and to shorter the respawn time.

I use Ignite and Flash with Caytlin, for geat damages and surviability help. Also, you can take Clairvoyance, because it helps the others champions to gank champions and for your Ultimate. Ghost can be great too, chasing down enemies or running away from ganks.

You don't want to take Clarity, because you don't need to use a lot your skills and you have mana regeneration. Don't choose Heal, lifesteal does the work.

- She's better mid, because of her abilities that deal damages to only 1 enemy. She's awesome in 1 vs 1. :)
- If she's bot or top, you better hide in the brush, making her passive powerful. Also, put some traps near you, so the Melee Fighters will not touch you.
- Put a trap in front of you, when you run away from a champion, so it will make him change the path to chase you down.
- Don't try to use your Ace in the Hole in team fight, because it could be easily interrupt and/or it could hit another champion, not the one you want.
- In team fight, do a lot of trap and attack the mages and other carries champions to seriously injured the enemy.
- With Piltover Peacemaker, be sure you previously practice your shot, to know the range you have with this skill.

To finish, I want to say that this is my first build, so comment it, because I want to be better and better. Leave everything you think about it, and sorry for the vocabulary, because I'm weak in English. Sorry again.

So, in conclusion, Caytlin is an awesome Ranged DPS champions, with great skills and a good passive. She's easy to play and easy to customized to your needs. I know, this build is short, but it gives a good summary of the kind of play of this champion. Have fun to play her and don't omit to comment this build. Thanks for watching and I hope you'll enjoy it.