Here's a pic of one of these neat-o tents Elena uses:
The whole "procedure" takes about 30 minutes tops, and can be modified to fit your comfort level. I spray-tan topless, and although initially it's a bit awkward (i haven't whipped off my top in the presence of a stranger in quite some time ;) -- the thought of tan lines helps that fear evaporate and most of these techs have seen it all and really could care less.
This is my second spray tan, so naturally, I consider myself an expert.
Things to know:
1) Don't spray tan on the day of your event. First off, the tan is sticky and smelly -- not vomit-esque or anything, but a weird sweet tanning smell. It's reminiscent of the smell of tanning parlors, except that spray tanning is actually safe and not a totally known carcinogen.
2) Another reason not to tan on the day of your event - the tan itself just after the spraying is not the finished product. I bugged the f out the first time i got a spray tan (before our honeymoon) because my face was dark - like darker then i ever get from normal beach activity - and it was a tad orange-y. I felt oompa-loompa-ish, but then I took my shower. TONS of bronze went down the drain and when I emerged, I was me, just a little more tan. Definitely something to keep in mind for your own tanning experience.
3) Get your mani/pedi BEFORE you tan, or if you don't, just do a polish change. Soaking your hands or feet will mess with your tan, so you look like Mickey Mouse with his white hands and feet. Same goes for massages, exfoliations, etc. DO IT BEFORE. You've been warned :)
4) Don't plan any activity where you want to look good whilst you wait for your tan to dry. You can't shower for 6-8 hours. Be aware. Also, you should not wear deoderant, or have any lotions/moisterizers on your skin on the day of the tan. So, if you can go in the morning, obviously this will save you the trouble of smelly pits and dry legs.
All things considered, when you emerge, I can assure you, if you get a good technician, a spray tan is a lovely thing. It usually lasts a little bit over a week, give or take a few days.
NOTE: At the tanning salons, they freak you out about using lotions containing alcohol post-tan, saying they will turn your whole body orange, etc, etc. I use ivory soap afterwards, and I don't really change up my lotion, and I've never turned orange. Of course, they will tell you they sell lotions that will help extend your tan, not turn you orange, change your life, etc, but be warned, you really don't need them. ALSO, the other day, I was behind a girl who was buying the JWoww tanning lotion, and I nearly vomitted to hear that they go for over $100 a bottle. I don't know what could possibly be in that bottle, but I do know $100 is too much for it.