1. Don’t…expect Ios / Mykonos.
Santorini is not a party island (necessarily). Yes, you will find clubs in the towns of Fira and Kamari (and, to be honest, I’ve had some big nights on Perrisa’s beachfront) but Santorini is not famed for its round-the-clock partying the way the islands of Ios and Mykonos are.
Do…love Santorini for that very reason.
Part of the charm of the island lies in its relaxed, have-a-frappe vibe. If you want a party, you’ll find one, but I suggest you take off your watch, put your feet up, and just savour the slow pace.