I just would like opinion on this. I have known this girl for a long time but never really talked. I am pretty sure she is interesed (strong IOIs) but I never made a move.
Last week-end I got her # and went out with friends (her included... we talked a little)
Yesterday, I called her and she didn't pick up, I called her back 2 hours later, she picked up and told me she was working and would call me back (it was already late 10:15pm), she was almost out of work.
She never did call me back.
I think she was just too shy or it was too late and its a typical situation of girls don't call... I am thinking about calling her back tonight for a date...
What do you guys think?

in these early stages, when a girl says she will call you back, most of the time, she won't. learn from this so that next time it happens you say, you know what i'm gonna be busy, i'll call you back on ____day.

regarding this situation, its hard to gauge how long to wait before you contact her again. i'm not sure how much you spoke before this, so i think the safe bet is to freeze her out for at least 2-3 days and at most 2 weeks.

also, don't be too pushy about setting up a day2. this puts too much pressure on them, and makes them more likely to flake. just talk to her about her plans and your plans and if you are gaming her properly she will give you some kinda signal that she wants to hang out. try not too appear needy.

I would wait at least 3-4 days then catch her when she is not likely to be working.

And if she goes out again with you it sounds like you need to get the kino going if she is giving you signs. Don't change yourself completely from the first date to the second but definitely get some contact going.

I think you should just call her back after a while and make it seem like you just called her back spontaneously and it had nothing to do with your previous game of phone tag.

I have an old friend of mine who's a girl and she always forgets to call me back, I know she doesn't hate me.

You don't really have anything to lose in that situation anyway.