Caitlyn is one of the most harrasing character early game, she is flexible amongst her different utilized abilities.
I have decided to write a build on Caitlyn to show my affection toher, she was the first champion I bought and until now, the most useful I possess. Whenever there are promos in League of Legends PH where there are required victories to get prizes, I use her most of the games to win.
She is easy to master, but hard to adjust since the most important aspect with her is positioning, especially to where her range can affect on a minimum amount of hits unless she has a red buff, for the slow.
Just a tip for everyone and I'm not sure if it would work on you: I always try to read a character's background rather than its advices on build websites like this, it was always a pleasure whenever I read how a character's life progressed until they arrive at the League of Legends.

Pros

Long-ranged
Strong base damage
Easy Farmer
Deadly when fed
Highest Physical Damage base Ultimate
Excellent against squishy characters
Unique design and gameplay graphics

Cons

Targeted first at Team Fights
Limited escape abilities
Squishy late game without frozen mallet
Ultimate can be blocked
Ultimate can be disregarded by champions like

Shaco , Sivir , and Tanks
Her skin colors are very noticable

I have not been a real fan of Runes until I reach 30. But for now, I focused on Armor Penetration, Attack Speed, and Critical Damage to maximize all possible offensive output.
See Cheat Sheet above.

Offense: 24
I maximized all offensive masteries whenever possible, although you could always not add Havoc since this mastery is not necessarily needed for Attack Damage Champions.
If you are using a Summoner Spell that falls under Summoner's Wrath , then go for it and do not add to Butcher instead if you use Flash and Teleport like mine.

Defense: 5
I focused on the armor of Hardiness since it was all that I was aiming for.

Utility: 1
Summoner's Insight for Flash and Teleport utiization.. obviously.

Instead of a Doran's Blade ,you may also start with a Boots and health potions if you are taking a mid lane or solo top for a very powerful harass input and optimization over the enemy's way. Although, I prefer Doran's Blade since this gives a playsafe type of early gaming. Disappointed with the latest nerf patch of 100 HP to 80 HP, though.
The item build is pretty much balanced with a double Bloodthirster for an exchange of life instead of adding a life item. Matched with the double Phantom Dancer for the Life Steal maximization.
Infinity Edge is the main core item in this build if you are regarding this to your runes. IT will give your runes its true meaning over its small amount.
I finished up with a Madred's Bloodrazor with a big IF you are facing a fed tank that is intimidating, but if you ended up as a powerful chaser, then I suggest you go with a Frozen Mallet thinking of its great Health addition.

I consider one of the best innate skills throughout the game. This, partnered with Piltover Peacemaker is a very scary farming ability or when you prefer, jungling.


This is your main harassing active skill in addition to Headshot especially when in an out-of-range with minions to a single enemy champion target. This may be opt to be used as a farming skill, too.


Better place these on very steep places where your enemies would be like "No choice *shrug*" or I prefer, when in laning, doing the known three trap near the enemy tower to intimidate enemy champions or placing on brushes to prevent ganking.
I also put this in middle or behind, mostly, when there is a team clash. May be also used as an escaping tool by measuring in estimates where it'd be active, when you are being chased.


This skill, I never used this to slow enemies BUT to move forward. When you are chasing someone, this could grant you a one-attack advantage that could decide his fate, you know *wink* ;)
This is also seen when Caitlyn's are really let us say, a prowess. Flexibility as a utilization or escaping tool. Good practice comes with experience.


I think this is pretty self-explanatory.
One tip by the way: Know your allies, trashtalk happens when you steal a kill. If you know what I mean. Hihi

These skills used in a productive way in saving mana can give you Caitlyn's True Power! Not with a long shot!

Pretty much every man's best Summoner Spell.


I prefer this than any other secondary summoner spell. Exhaust and Ignite follows in second. Try it, it benefits especially in cash I promise. Teleport is a must-have especially when you are impatient onto going to your lane. But that really isn't the real reason behind my dominance over others. With this build, you'd get tired getting near the enemy's base with other spells.


Very useful when chasing annoying wackadoodles that escape you. With this, your grasp on the enemy's death string would be at its maximum. This is a great advantage over one on one battles with Caitlyn
Although, I do not really like to use this since I'm the flaming laner and surprise type.


Of course, who wouldn't want a true damage over time finishing summoner spell. This is best used and partnered with Ace in the Hole, no escapes guaranteed!


A Caitlyn chaser is really deadly, with a turndown advantage of runner. But you wouldn't want this if you have mastered her positionings.

Others, are less acceptable.

That sums pretty much most of it. I admit that not everything here is pure originality since I before used Mobafire builds too until I formulated my own.
So, I am really sorry for the imperfections. This is written on a 45-minute basis.
And sorry for the bad english, I'm bilingual.
This build is made by pure experience and attained knowledge. I play LOL PH.

Please, mind you, try it out before voting and I accept compliments or violent reactions.