ask for the date
I'm inclined to agree with HPNOTIQ. It is a good question.
It all depends on the situation. Asking for the number to test IL is one thing if you want lots of numbers which may or may not equal choices. It was going to start out by saying that asking for the number first works well in a club, but you know what? It doesn't matter. Ask for the date.
If you're getting up the nerve to ask for something, ask for the date. I think some women see asking for the number as AFC behaviour as well. I've seen enough posts here where guys are trying to get up the nerve to call the chick, wondering what to say, when to say it, whateva - all in trying to set up a date. Ask for the date. At least get rid of the implicity that asking for a number conveys. Be direct in asking for the date. TELL her you want to take her out for coffee, movie, jello wrestling. Then tell her you need her number.
Chicks phone numbers are not business cards. You definitely can judge how worthwhile an event was, by how many business cards you come away with (it's called 'networking'!), and not by how many of yours you gave away. But "last night I had my game on and came home with 7,432 numbers" is nonsense in my book. After a few beers, how the F are you going to remember all the chicks anyway? Come on! I KNOW this has happened - who will own up to reaching in their jeans the next morning or days later, pulling out the number (ahh ... the prize!) of a chick you met the night before, and wonder wtf she looked like or even said?!!
Back to situational differences....if you still think #first, it is still cool to get the date first if she is just around the corner, down the hall or wherever. You did good, coin.
Ask for the date. If the IL is there, the number will follow.