The entire point of this build is to kill your opponents before they can get a hit in. Attack speed combined with damage drops your opponents health fast, while life steal keeps you at full health.

Pros:

High DPS (Damage Per Second)
Great for farming/pushing
High mobility
Good for back-dooring
Easy to play

Cons:

Squishy
Vulnerable to being focused by more than one opponent

I go with an attack speed and dodge setup for my runes. Attack speed works best for yi because he is based on speed. Dodge runes add a bit of survivability for you, and some frustration for your opponents, as their attacks will be constantly missing. Dodge runes have saved me more times than I care to admit to.

I use Ghost because it can be used to pursue or flee from your opponents if need be. I also use Cleanse because yi is squishy and needs to be able to keep attacking in order to stay alive (this is where life steal is important). Cleanse can best be used to remove stuns, fears and blinds. Slows should not be an issue, because Highlander's activation prevents Master Yi from being slowed.

First item to buy is vamp scepter. It helps keep you on the front lines during early laning phases of the game. Upgrading to emblem of valor as soon as possible increases survivability. Next thing to buy is berserker's greaves because, attack speed is the way to go with Yi. Next up, grab a B.F. Sword to get some damage in the build. Then, more attack speed with phantom dancer and upgrade your sword to an infinity edge. By this point in the build, you should be able to kill anyone in sight. Next two items should be tailored to your opponents. If you are going against a high armor tank, then get a last whisper for armor pen. If you face high hp champs such as mundo or cho'gath, get a madrid's bloodrazer. If You are going against spell casters, perhaps a banshee's veil is a good idea. Otherwise, just add more damage to the build by getting bloodthirsters, black cleavers, or infinity edges.

Alpha Strike: Great for farming, and good for last hitting or chasing low-health opponents. Can be used to turret dive, but should only be used if the opposing champion is at low enough health that they will die from Alpha Strike.

Meditate: Helps keep you on the front lines early game, and its +300 armor and magic resist are great for withstanding nukes.

Wuju Style and Highlander: Can be used well together to take down turrets and kill opposing champions

Highlander: If absolutely necessary, can be used to escape combat. Should never be used to get to combat faster, though. If you feel the need to run faster to get to a fight, use ghost instead.

General Advice: Master Yi is a very good backdoor champ. While team battles are taking place in mid, try pushing one of the side lanes if you aren't needed in mid. Yi's high damage output and superior mobility make him ideally suited for taking down turrets fast and escaping ganks when necessary.