OK. You have successfully obtained the real phone number and/or email address of a human female and want to contact her. The first question you need to ask is when to actually do it.
Current dating wisdom states that you should not call the next day. Personally I feel this sort of thing really depends on the circumstances in which I met the girl and/or how the opening conversation went. If we met while doing something fun and semi organized (hiking, vampire LARP, charity rugby match, etc) or perhaps the conversation flowed particularly well you might consider calling the next day (late afternoon). However, odds are if you are in need of this blog you probably don’t have a great barometer for measuring this sort of thing, so perhaps you should stay away. It is easy to let your eagerness and/or insecurity let you fool yourself into thinking the conversation was better than you think it was and call too soon.
Never call the same day you got the number. If you want an example of how badly that can go watch this scene from Swingers. Painfully funny.
Anyway, I would recommend as a guideline to call or email within 2-3 days of getting the number. More than that and you seriously risk pissing her off or worse, being forgotten.
You think you have it rough? Abe here had do figure out the best time to send a telegraph (image courtesy of the steam punk t shirt category).