Pretty much what you want to do is spam your volley as much as you can early game, to farm. Which is why the mana regen seals really come in handy, i used to use cool down reduction glyphs as well, but it really doesn't make too much of a difference, attack speed does.
Cooldown late game isn't really helpful, since late game your basic attack will be stronger then all your abilities.

simple build really, high crit

i seen other builds saying high crit isn't reliable, but i beg to differ

high crit, even with just a Zeal & Infinity Edge early-mid game makes a difference, each crit will do damage of about 400 with just those items, your crit chance at that point is about 60% which is very good, you will get at least 1 crit per 2 hits most of the time, and with high attack speed, that makes a difference

armor penetration isn't as useful, let's say hypothetically u can get 100 in armor pen, that is only 100 extra damage, and thats if your opponent even stacks armor, no armor=wasted armor penetration

full build crits without minion kills will get you about 900 ad thats about 2800 ad per second

if you are in lane against someone who has more range then ashe(cait, etc.) start off with vampiric sceptor, u will need the lifesteal to recover a lot without leaving ur turret defenseless by returning to base, if you are turret hugging, then get the doran blade after, boots can wait, since you are just hugging

hex is an optional item, it has an up and down side, the good thing is, it will help u with life steal and spell vamp, really it works great, this way you dont need armor or more life or magic resist because 1 hit with an arrow will recover AT LEAST 1/4 of your life, with high attack speed your almost invincible on 1 on 1's, even on 2 on 1's......

the down side though, is you got to sell your boots, which will leave your movement speed at about 390, which is very low, but late game u might not need speed as much if your opponents is just defending base, or vice versa, (whatever you do, do not sell Blood Thirster for Hex, Blood Thirsters are really useful)