Exfoliate. Since self-tanners react with the upper layers of your skin, if certain areas have thicker skin than others, your "tan" will be more concentrated there. In other words, you'll be splotchy. Buffing your skin with a scrub evens the tanning field. Give scalier areas, like your knees and feet, extra attention.
Moisturize. A thin coating of moisturizer smoothes the surface of your legs and prevents streaks. It dilutes the self-tanner a bit—but what you lose in intensity you make up for in uniformity.
Apply. The directions on the bottle might tell you to start from your feet and work up—but don't. "Think about where the sun hits," says Kara Peterson, who trains aestheticians in the art of fake tanning at Clarins spas. "Start off in the middle of your thighs and the middle of your calves and blend out." Your feet and knees should get only whatever's left over. Also, do the job standing up, says Peterson—when your knees are bent, you might apply too much to the stretched skin.
Shimmer. After your self-tanner has done its work, blend a slightly iridescent lotion over the front and back of your thighs, along your shins, and down to your feet. "The strategically placed shine has a slimming effect," says Linda Hay, head makeup artist for Victoria's Secret Beauty. If you have olive or dark skin, you're lucky—just do step four.