As someone who successfully snagged me an INTP on the first date-but-wasn't-really-supposed-to-be-a-date:
-Be blunt about your feeling. If you're an ENFP be flirty as can be. Play up your natural charm. They rather like blunt things I've found out.
-Be honest. INTPs also seems to have a knack at sniffing out any BS.
-Be intriguing, but don't be false.
-Talk. I've found INTPs like to listen and are really good at carrying on conversations if you start.
-If they seem to be restraining themselves from making a move, make the first move. If they don't run off screaming I'm pretty sure they like you. Or are scared.
If all else fails I've found common bait amongst INTPs : Food.