Avoid skin on skin contact until you rinse. Crossing ankles, knees, touching your tan, etc can alter development. The tan can transfer from one area to another resulting in an uneven tan, sometimes even removing the tan completely.
Fragrances and perfumes with alcohol can speed fading. Spray fragrances on clothes, not directly on skin to prevent premature and uneven fading.
Applying moisturizer helps prolong the life of your tan by providing hydration and preventing dryness/flaking which can cause premature fading. Look for lotions without mineral oil or harsh sulfates.
Do not sit in sweaty, tight clothing. The sweat and friction may cause an uneven, premature fade by breaking down the tan if left on for extended periods of time. Rinse off post workout, making sure the salt from sweat doesn’t sit and break down your tan.
Tan doesn’t provide sun protection. Wear SPF 30+ and reapply frequently when going in the sun.