I'm ninteen so my biggest complaint in SF is that 99% of the places to go see music or go dance are over 21- which is great if you are. the places to see concerts if you under 21 but over are Maritime Hall(18+), the Warfield, the Fillmore, Orpheum theater, the Cow Palace, and for smaller shows- which i like better- Ameoba Records,Slims, Mission Records, the Brainwash cafe and laundrymat. For dancing, CityNights(18+) on harrison and 3rd, 330 Ritch(18+ on select nights) and if you like raves go to F8 on haight between stanyon and shrader and they'll tel you where to go. My favorite places to go is dance mission which is like an undrground rave where people pracice for fire dancing every Tues night from 9:30- midnight.
If you do poi or something related you will be in heaven. I like to do pi under the black light and I learn so much there too. It's only a donation to get in- the people are so chill. The area is kinda sKetchy but just act like you know where you're going and you should be fine.