Well the reasons are...

If I call the day of in the evening it'll sound desperate which i'm not (or i'm really digging her which isn't the case...I like her but doesn't mean i'm all crazy about her type of deal)

If I call her the following day it feels too soon to be talking about it. I want to give her time to think about what we did and reflect upon it. I also like to sit back and think about what we did also. Hang out with friends, maybe talk about it with buddies etc. If I called her the next day it might also give the impression that hey, this guy doesn't have a life type of deal and he's just always after the 2nd outing (my 2 cents anyways).

Now if i called on the 2nd day in the evening it gives time to clear out the thoughts and all. Not only that you can also bring up some topics that were talked about and see if she remembers (yes guys test girls too lol). But it also gives you sometime to iron out what you want to do for the 2nd date. Cuz if you went out on say Sunday, wait 2 days it'll be Tuesday and you'll get an idea if something is coming up for Friday or the weekend etc.

What do you normally do Wyndhy?