done it MANY times - steps to take:
1) exfoliate and shave in the morning. do not put any lotion on. and very little makeup.
2) go get sprayed.
2a) put the lotion they give you anywhere you don't want tanning spray, like between your toes (where it can build up), heels of your feet (trust me), palms of hands, etc. really lather it on.
2b) they give you disposable panties - wear it as a thong and low rise (twist it) so you don't get unwanted tan lines. and let your boobies hang, but lift them to get the spray under them.
2c) it will shock you (it's chilly) but let it go. here is the thing:
IT TAKES 3 DAYS FOR THE COLOR TO LOOK NATURAL
So, ask for it to be "regular tan" and you will look totally orange, but 3 days late you'll look amazing. it will fade in the follow 4 days.
OR
go very light if day before an event
OR
go darker if you want it to last through a vacation.
2d) Afterward make sure you dry yourself with the blowdryer thing SUPER WELL. HINT: takes a washcloth/towel and very lightly "feather" it against your skin as your dry (light swipe at the skin) to blend it naturally and even out any splotching from an unever coat. THIS IS KEY TO A NATURAL LOOK.
2E) MAKE SURE YOU ARE TOTALLY DRY before putting on clothes. Make sure you wear super loose clothing like a very loose dress or sweatpants and a big t-shirt
3) Afterward avoid all water for 24 hours. no showering, no dishes, nothing.
4) when you get home look in a mirror. if you notice splotching feather it with a towel asap. if you face looks too dark, rub it harshly to get off extra tanner. you can always use bronzer. actually i always say "go lighter on my face" b/c i'd rather use bronzer than look like and oompa-loompa.
5) check in mirror again in 2 hours, 4 hours, etc. wear loose clothes to bed.
6) shower the next day as usual, but avoid harsh body washes, DO NOT USE EXFOLIANT. But. if there are any dark areas, scrub that shit out. you might also want to use alcohol on a washcloth, or in an extreme case go to Sephora and buy self tanner remover.
7) in 2 or 3 days you can get a pedicure, but tell then not to do anything above the ankle or else you will loose your tan. ALSO, NO POOLS - chlorine will take it off in the first 5 days.
8) ENJOY YOUR SEXY TAN