Hey there
I'm a beauty therapist - here are my recommendations.
Look for somewhere that does SunFX spray tans, they are brilliant and chemical free. I've never once looked orange and I've used this product for years and years.
I always get mine the day before, but you can get it two days before and it still looks great, and that way if there is a problem you have time to get it fixed -just moisturise the skin after you wash it off to keep it hydrated.
The longer developing tans look better than the rapid tans, so unless you need to get a rapid developing one for some reason, stick to the original tan.
Exfoliate gently the day before, but don't go crazy and over exfoliate either.
Wax or shave the day before the tan, else it can remove the colour if you do it after.
I also suggest moisturizing daily leading up to the tan so your skin is hydrated and the tan goes on and develops better. Dry skin will look darker and patchy.
I always tell clients to get a tan a few weeks before an event as a trial if they have never had one before just to check if they are happy with it, but again, I've never had a problem with the sun FX tans