I first did it yesterday, and I'm 17. There's a smoke shop that says "YOU CAN'T COME IN UNLESS YOU'RE 18" or something, but I look old enough and have bought from there before. I got some 5x "Purple Sticky Salvia" because it was the cheapest, and I was paranoid the guy was going to ID me, but he didn't, and also sold me a butane lighter for pretty cheap.
I'm still trying to get the hang of lighting it correctly and stuff, but I smoked a third of what I got yesterday with some weed and was pretty fucked up.