Welcome to the wonderful world of spritz tanning!! First what you want to do is shop around. Locate salons that offer the spray tanning and find out cost per visit and, most importantly, how long it takes. You have to hold your breath the whole time so make sure that you decide on a salon that won't take longer than you're able to hold your breath for. The one I used took only 6-10 seconds... the best on the market! Now, most places will show you a short introductory video on your first visit but if they don't, here's some pointers. It's a two-roomed booth where you can get undressed and then sprayed in the other part... also there's a button you push to start the timer, and it'll count down probably 15 seconds and then start spraying, so while you're in the spraying part, you can watch it count down and prepare to hold your breath. You'll be given a cap to put on but don't worry about covering your hairline, or else you'll have lines on your forehead (it's ok for the stuff to get in your hair). Keep moving while it's spraying to be sure that the solution has had an opportunity to be sprayed on every part of your body. After it's finished spraying, rub (in a circular motion) the solution in with your hands... be sure to do this EVERYWHERE!! When you step into the changing room part of the booth, pat the rest of the solution off and wipe the bottoms of your feet and palms off, then dress. They should give you an exfoliating scrub and a washcloth... go into the bathroom and use that to scrub the palms of your hands. DO NOT put your hands under the water, or it'll wash the solution off. You just want to get a teeny bit of water and exfoliating soap on the cloth, and be sure to get between your fingers and where a normal tan would stop on the sides of your hands (for beginners, it'll probably look a little weird the next day, but unnoticeable). Don't do anything that will get you wet (swimming, showering, rain, sweating) for at least 5 hours afterwards. As time passes, you'll start to look a little orange. After 5 hours has passed, you can take a shower and you'll notice that the rest of the solution will come off in there. Be sure to pat dry when you exit the shower, as well. The tan look should last 5-7 days. When I did it, I did it mid-Sunday, showered Sunday night, and was at peak Monday (day 1). Day 1 and 2 are probably the peak days, then it gets a little lighter after that. Depending on the salon's version of the booth, you can reapply it whenever you feel it's neccessary. The salon I settled with had a 2 visits for $20 deal but I've seen it get as pricey as $35-$40. The smell is kinda funky but it's not gross, and it just feels like you're being sprayed with cold water. But it's definitely not something you want to do on a busy day... you'll want to do it when you've got half a day to spare, so it gives you time to get it applied and the appropriate amount of time before you shower cuz you'll be slightly orange before then. I'm not aware of any dangers, besides inhaling the solution while it's being sprayed, and I don't think it'll cover scars or stretchmarks. I had a funky tanline when I did it and it didn't cover it completely, but it helped even my skin out. Now veins might be a different story, depending on if they're spider vein thingies or regular ones just popping out (I'm pretty sure it'll cover spider veins).
Phew... sorry this was so long but I'm sure you'll find it very helpful to walk in knowing what's going to happen and what to do.