I did some search and surprises me the fact I haven´t found this question btw I think it should be on the FAQ. Oki anyways, getting the girl for the night and her phone number ar no big deal for me. What comes next is mostly the same crap I get no answer later, they always have some excuse, man time is manageable if you really want to do something you manage time. So I got basic questions:
*When do you phone? How many days, hours, years later?
* Do you try to set up something on the first call or you drop it by a next call using the first just as a thermometer?

If you got the number late in the week, phone on Sundays. People are always home on Sundays, especially early evenings. If you got the number on Monday, just pick a day good for you. And you can always ask for a date on the first call. Just casually throw it out there. "Hey, let's get together sometime this week" is all you need. Let her recite to you her scedule first and go from there. If's she busy, play it off and just say "we should get coffee, that'd be fun". If she says she's busy again freeze her out. Say, you've got to go but it was nice chatting. Call again a few days later and repeat.

Hope board "chatting" is not an issue so I keep asking, problems which arise on this approach:
Parties are usually on Sat to Sun. If I call Sund I sound desperate, if I wait I call on the week problem like to schedule something too ahead.

If she's into you and she gave you a number, she wants to talk to you. I don't suggest buying into all the 3-day rule junk. The only way you'll give off any desperation is if you come off that way in conversation.

Problem is that 99,9% of girls are into you for one night. Seems hard for me to get the step further.
EDIT: And again do you try a set up on the first call?