Some people build certain champions as "glass cannons". I find Yi to be the perfect champion for my build- the "glass race car".
Remember- this is another of my troll builds, but this one works quite well.

Excuse the masteries, I didn't see many for movement speed. Change them freely.

Must have:
Ghost- Move speed. 'Nuff said.
Choose between:
Flash- Good for getaways if they have CC that can counter your speed.
Exhaust- In case they have a Rammus or Master Yi that's almost as fast as you.
Not recommended, but okay:
Ignite- You aren't playing offensively.
Heal- You have Meditate.

Mobility Boots- The passive on those gives great move speed.
Phantom Dancer- Move speed, crit chance and attack speed? Sure.
Zeals before Phantom Dancers?
Thank my brother, DLLrul3rz for that piece of advice. It's just more efficient that way.

Personally, I say this is the most important chapter- master it before you play.
When you play a troll character, teammates hate you. You just can't let them get at you.
"Singed: Noob Yi
Master Yi: How so?
Singed: NOOB
Master Yi: lol, umad?"
Another important part is retaliating, but remaining calm. For example:
"Singed: I hate noobs
Master Yi: You hate urself? sad.
Ryze: lol
Singed: I'm Yi
Master Yi: Great, now he's delusional.
Singed: Fast and useless
Master Yi: Beats ur 'slow and useless' technique"
And if it keeps up, and you're getting upset?
"Master Yi: All in favor of reporting Singed, say I"
The best part is, they're the ones that get low scores and high reports.

Above chat from my last game.

I can't go into enough detail in this chapter, but I will say this. Don't let them report you; they have no reason. MAKE SURE TO SAY SO. This way, even if they do report, the tribunal can see your reasoning. I would know, I work in it.

Early Game

1st thing to do- RUSH TOP. And I mean rush, as you'll be the fastest on the team- well, maybe next to Rammus. After you get top, run to their mid. When they go after you, you outrun them.

Mid Game

Keep up this trolling all game, no matter what your team says. They threaten to report, insult your score, complain to enemies.

Late Game

Ghost and ult late game can bring you up to 1000 move speed. I've only ever seen this build up to the 4th Phantom Dancer (950 speed). Near the end of the game, say to all "Why report me? I was distracting them so u could cap. U just too noob to cap." (last part optional)

Now, you won the game! If not, complain about your "noob team not cap when I run in", and threaten to "report for not capping and for raging". Again, this is optional.

I am not responsible to damage done to your account, team or K/D ratio. Side effects may include bad kd, reports, loss of account, loss of nexus, and vomiting. If these problems persist, contact a doctor or better Yi guide.