Melanin is the naturally occurring chemical in all humans and animals that results in colour in the skin and hair. (Only albinos are born without melanins, which is why they lack skin pigmentation and hair pigmentation.) The darker your skin, the more melanin you have. Melanin is a natural protection against the sun's harmful ultraviolet rays. However, spending hours in the sun means wearing sunscreen to protect your skin, no matter how dark your complexion. When you get sunburned, your skin and your melanin have been damaged; both need time to recover.
Wear sunscreen before going out of the house. After getting sunburned, when the melanin is less effective because both it and your skin have been damaged, sunscreen is a vital part of protecting your skin from further UV damage and allowing it to recover. (A sunburn won't turn into a tan because the melanin was damaged at the same time as the skin was damaged.) To replace the melanin, your skin must have protection against the sun until the sunburn fades.
Put on tanning lotion both before and after any indoor tanning session. If you decide to work on building up a tan, tanning lotion for indoor tanning is a necessity; it keeps the melanin working to its optimal ability and prevents your skin from drying out. If you tan outside in the sun, you should wear an outdoor tanning lotion instead. The lotions will help minimise the risk of a sunburn and damage to the melanin; the tanning will help build up your melanin by increasing your skin pigmentation.
Allow the tanning lotion to sit your skin for at least four to six hours before showering. Showering too soon makes the lotion ineffective; your skin needs enough time to absorb it. If the lotion isn't absorbed, its positive effect on your melanin is limited to the time you're actually tanning.
Schedule tanning no earlier than 24 to 48 hours after previous tanning sessions. Waiting 48 hours will avoid accidental burning from the UV rays and allow your melanin to recover; this is especially important if the skin was slightly burnt in a previous session. Your melanin is damaged and becomes less effective when you get burnt; only time can rebuild and repair it.