Gently dry the area you will be self tanning, and DO NOT apply a moisturizer. Instead, begin by applying a small amount of self tanner and gently rub into place, making sure to keep your fingers tightly together. If your finger are separated, it could cause streaks in the tanner. Lancome makes a really good self tanner called Flash Bronzer Tinted Self-Tanning Mousse(Compare Prices), and Mystic Tan makes a complete at-home kit (Read Review).
Do not apply tanner directly to feet, around eyes, or over rough areas of the body. Instead, apply the self tanner to all other areas and then follow the smoothing directions in Step 3.