This here is my first build, and after reading multiple other builds I put together something that has worked for me. It involves lots of attack speed, ending up between 2-2.5 attacks per second, and the proper amount of armor penetration.

The rune build is mostly attack speed. The more shots you can get off the greater the chance of survival, both offensively and defensively. This is because not only are your lowering the life of the opponent quickly, you can also run and shoot faster making for a quick getaway.

The build of 22/0/8 is strong for more attack speed and armor penetration and just flat out more damage, with haste in the utility tree for multiple uses to improve the ghost spell.

The item purchases focus on a little bit of attack speed first with armor pen. to follow. Then more attack speed and damage/arm pen. to finish it out. The items are quite pricey but I have found with the number of champion kills I am getting, the items come rather quickly.

The skill sequence is pretty self explanatory with the one point in hawk shot to get the advantage of charging bushes and the shadows.

Make sure that Frost Shot is only active when attacking a champion.
Spamming Volley is very situational. Mana should be taken into consideration as well as health pools and number of additional champions
Hawk Shot is excellent if you suspect enemy champions in the bushes, or around the corner, or simply off in the distance. That is the reason it comes in handy at the low level but only the first rank.
And your ultimate should be abused. It has a decently short cooldown and does decent amount of damage, on top of that it can't hit minions and flies across the map. It is ok to shoot it without the intent to kill just to lower the enemies life and wait for it to come off cooldown the next time around.

Ghost is very helpful especially when retreating or getting off that last shot and escaping the tower. The only other two I consider are flash and teleport. Teleport comes in handy when returning to purchase new items and wanting to get back into battle quicly.

Pros

Attacks very quickly and deals lots of damage
Good for get away with the ability to slow and move fast
Can catch enemies making for an escape with ultimate or ghost
Generally gets killing blow because of massively quick attacks

Cons

Still quite squishy, generally targeted first
Slow beginning to the game
Items are priced rather high

Excellent helper champion given the slows and quick attacks. So if there is a champion you are having trouble with killing, have a partner go attack and just make sure to crowd control the opponent with your ultimate and frost arrows.

And as always, definitely an excellent creeper. Stick to a lane until you feel comfortable, generally with a little more attack speed, and maybe some armor pen. Generally you can bait enemies in with your squishiness and then demolish them with your ultimate stun.

Overall, it is about abusing your ultimate stun, and the slows are crucial. The armor penetration will help a lot, and the passive critical hit chance from the items will make for some crushing blows. I have seen my enemies health pools drop quick then I disappear before they can even get help.