I'm under the impression that the general public knows the three day thing. It's common, I've heard girls and guys talk about waiting three days, with no knowledge of Pick Up.
I generally call when I'm feeling it. Day after, second day, I don't think it matters so much (like most of the guys have said already), provided you aren't sounding needy or lack confidence. If three days is the general rule among people now...be the exception to the rule! You get AFC's who wait three days because their friends tell them to, and they build her up so much in their mind that they can barely talk without their voice cracking.
Just be that same guy she met when she gave you her phone number, it's what she's attracted to. If she is attracted to you in the first place then she's already waiting on your call
~Muse