Caitlyn is a High Damage AD Castor type Champion. With High AD Ratio's on Q/R and a Damaging Passive she can relly bring the pain to the enemy team. Alot of people build Caitlyn as a Machine-gun DPS type but this is a slower play style aiming at her ability to deal high amounts of damage to any type of champion Squishy or tank.

Marks: ArP Runes lowering that Armor Early game allows for greater Damage dealing.

Seals/Glyphs: Crit Seals and Glyphs are what I use. It seems a bit unorthodox on Caitlyn but when your doing 1200+ Crits end game you see why.

Quints: I suggest Movement speed runes mostly. They allow faster movement thru jungle and lanes. XP Runes are acceptable too if you like that sort of thing.

Start with Vampiric Scepter you will be building it into Executioners Calling.

Boots of Swiftness are a must for manuvering. Boots of Mobility also acceptable.

When Building Trinity force just get sheen till you have 2 items slots left over.

Inifity Edge is Important to the build increasing Crit Damage.

Madreds BLoodrazor is your Main Source of Attack Speed as well as your ticket to taking down Tanks.

Your last item is more situational. Example if you have Jax get Sword of the Divine if they are mostly squishy get Bloodthirster.

Ghost/Clairvoyance.

I know CV is mostly used for Support but they won't always be able to drop it when you need it most. These are your Hunting tools. Chase and Vision. Use CV when someone runs a bit too far but still in ult range to snag that last hit. Or to check bushes when your over extending.

This is important, Champions who can Use CC are extreamly important in both postioning your target or stoping those wishing to black your ult. This build is mostly based around picking up escaped kills so don't be surpised if you get called a Kill Stealer now and again. Just do your job and kill.

So I am not sure if this is enough information but it is my first guide haha. I hope you enjoy the build and find ways to use/improve it. I level Q-W-Q-E-Q-R-Q-W-Q-W-R-W-E-W-E Ect. Happy hunting and may the winds favor your shot.