When you are out and ask a girl for her number, how long should you wait to call her?

Call her the next day. If you wait more than 3 days, it's kind-of rude, unless you have a good excuse. I can't speak for all of womankind, but I do appreciate it when a guy is up-front and doesn't play games...

That same night might be too soon! But the next day is fine.

I think if you were really excited about her, you should let her know it. So if you want to call her the same night...that's ok too. It is flattering to us ladies.

Definitely the next evening.. and then set something up for the next day - if she invites something sooner, then go for it. ;-D ...go get 'em tiger!!

You should call any time from the next day to 2.5 days later. And that's the truth.
Never call from your car after you dropped her off. Like...never.

Definitely the next night, if you got a good vibe from her. Smart, mature women will hate you if you pull the Swingers rule. It immediately smacks of "playing games."

The next day to tell her how much you enjoyed meeting her and to establish your credibility. It’s great karma to to make someone else feel great!!

I have always told my son, “Say what you mean and mean what you say.”

Also, don’t ask for her number if you have no intention of phoning.

wait a week or so.