Do's
Be casual and relaxed.
Complement her on her clothing, hair etc. Chicks love compliments.
If your funny be funny, if your not, don't try to be.
Drive the conversation towards her life, avoid talking about yourself to much.
On the off chance you get yourself a date, do something reasonably romantic and something you think she might enjoy.
Dont's
Don't follow her around like a love sick puppy, it's pathetic and she knows it.
Confess your undying love, that's even worse.
Make a public scene when you find out she doesn't dig you.
Make fun of a genetic defect (birth mark, lazy eye etc)
Actually making fun at all is pretty bad, though playfull teasing can go a long way.
That's all I can think of right now, but these are only ways of getting yourself noticed. If she doesn't like you at the first attempt, it a very rare occurance you'll get her to change her mind about you.