I met a girl at a party. When should i ask her out?

Sure call the girl ask her out...She is probably waiting by the phone wondering why you haven't called her yet....

mmm maybe ask her for abnother day so she could plan it and be ready

just go ahead and dont ask such simple questions...
just tell her- hai doll let's go for a coffee.

right away dummy!
she s gonna think your not interested cause you were just looking for a one night stand and getting her number was just being polite!
(dude, you have to think like a woman!)

Since u got her number, why not chat with her on phone and decided whether she is the right one for u before dating her out.

first call her and talk to her on phone.If possible arrange for meetings through friends but without letting her know about that.After 1 or 2 such meetings and calls you can ask for a date and be assured for a positive reply

Dont call her until like tuesday or wednesday... if she still seems interested, call her back like next monday and ask her out for friday or saturday.

Well, it depends on how the conversation goes. If she seems into you then go for it.
But definitely don't wait til Friday to ask her out!

if she gave you her number, you should just ask her out already.