Hey fellas, I'm Sam... I like to play Caitlyn, she's one of my favorite ranged AD's. Not many people play her since she gets out-shined a lot. Although I give no ****s. So here goes, welcome to my thoughts on Caitlyn.

This is all in my opinion, so keep that in mind.
Pros:
[*] Strong if played well.
[*] One of the longer ranges in League.
[*] An Ulti that is a guaranteed hit, maybe not the target you want. Still hits something.

Cons:
[*] Gets out done by many ranged AD's late game
[*] Not a 'Hyper Carry'

Alright so depending on the support you have, meaning either with sustain(a heal) or not. You have to make a choice.

A: Starting with Boots and three Health Pots
- You get Boots and three Health Pots of you're in lane with a support that has no sustain.

B: Starting with a Doran's Blade
- I'd only suggest getting this is you have a Alistar Sona Soraka or Taric

From there you can figure the rest of it out quite easily. You want to finish your Berserker's Greaves and get two Doran's Blade along with a Vampiric Scepter as fast as you can.
Hopefully you're halfway good at CSin' because you're goal is to get your Infinity Edge by about 25-30minutes. If not, you're not doing too hot. The only reason why I'm explaining

The last two items on there you can pick from, you need at least one survivability item. That just goes without saying. So your choices are;

A: Guardian Angel

B: Banshee's Veil

By end game, you should have the entire build... If not... Unplug your computer.

Now I may have set items down, you don't have to follow the order specifically. Remember to change your build based of the enemy team as well. Never follow a guide 100% that's for dummies.

Also, to those of you that think Thornmail is good on Ranged ADs you need to throw your self off a cliff.

I have runes set up to give me the best early game possible. So keep that in mid as you see what runes I use... Here goes,

Marks:
Greater Mark of Attack Damage x 9
I do this because it gives you the best start in my opinion. Armor Pen runes help you late game, but you build that **** in items.

Seals:
Greater Seal of Armor x 9
You're against another ranged AD bot lane, don't be stupid.

Glyphs:
Greater Glyph of Scaling Magic Resist x 8
These will help you out throughout the entire game, not only the mid is AP. Sometimes your enemy team has an AP jungle.
Greater Glyph of Attack Damage x 1
This just rounds you AD up to 16, so why not?

Quints:
Greater Quintessence of Attack Damage x 3
This is also a given for me, since the other possibilities are just ****.

Alright the standard Ranged AD Mastery page, 21-9-0 is what I use.
http://www.mobafire.com/league-of-legends/mastery-tree-planner#&tree1=0-3-0-1-4-0-0-4-1-0-0-1-3-0-3-0-1&tree2=1-0-3-0-4-0-0-1-0-0-0-0-0-0-0-0&tree3=0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0&v=2

Yeah this pretty much goes without saying.. Its the new meta for ranged ADs to take Heal since it gives them more HP. I don't really have much else to say on this.

So the spells I take are;

Heal

and

Flash

I see these to be the best bot lane, for the ranged AD.
Lets take a peek at the other spells...

Exhaust Can be useful, but usually the support takes that these days.

Ghost Just take Flash...

Revive No... Just no...

Smite Only in the jungle.

Surge If you take this spell, you're just dumb.

Teleport Not really needed, its only really useful top lane and somtimes mid..

Cleanse I would sometimes take this over Heal, but I would only recommend it if you know what you're ****.

Clarity Nope.

Ignite Nope.

Clairvoyance Hahaha no.

That pretty much wraps that up..

You must farm like a champ, force enemy to leave lane. Farm like a champ 100 every 10 minutes.

Alright, so you know since you're playing Cait you;re obviously going to be against another ranged AD.... Unless you're a ****ing ****** and go into some other lane.

Ashe You beat her early game, and if you farm well enough you can late game.

Corki Depends on how he builds and you play, he'll probably but **** your team late game.

Ezreal Non-factor lol..

Graves Lol he ****s everyone, just sit back and farm.

Kog'Maw Once he hits level six, be cautious for his Ulti... If you;re smart you can dodge it and make him waste his Manners.

Miss Fortune I honestly think she's super under powered, so no worries.

Tristana She's really weak early game, but don't under estimate her late game...