Exfoliate your skin thoroughly the day prior to your spray tan appointment and follow it up with a moisturiser.
On the day of your appointment, DO NOT apply any products to your skin (no moisturiser, deodorant, makeup or perfume). Any product applied to your skin will act as either a barrier to the tan or it may react chemically with the tan solution resulting in the tan becoming patchy or it may take on a slightly green look until you shower it off.
Make sure you have loose, baggy clothing to wear after your appointment as tight clothing will rub against your skin and may cause patches. This goes for bras as well.
Bring thongs/flip-flops to wear after your appointment, as shoes/socks will cause the tan to rub off/leave patches.
Ensure any and all of your hair removal (i.e. shaving or waxing) is done at least 24 hours prior to your spray tan appointment. Do not shave or wax on the day of your spray tan appointment.