My understanding is, and perhaps I'm wrong here, that the conventional PUA wisdom is that after a first date you should wait a few days before texting a girl.

I was reading about this on a forum (not PUA related, mixed male female users) and the consensus overwhelmingly seems, supported by both men and women, that you should text either the same night or the next day.

The general consensus among girls seems to be that they like it when a guy texts the same night and that if he waits 2-3-4 days that it feels like he's either not very interested, which would make them lose interest, or that he's playing games, which is also a turn off and that they'd drop a guy even after a good date if he texted a few days after the date, rather than earlier.