If the term "body contouring" makes you think of muscly body builders and crop-top-wearing pop singers, your mind is about to be blown.

Every time you get a good professional spray tan, they do some subtle contouring -- whether you realize it or not. That's because contouring takes a fake tan from flat to natural looking and makes your legs look half the size.

How exactly? It's all about optical illusions. "You don't want to look like you're contoured, just faint definition," says Tamar Vezirian, owner of Gotham Glow in New York City. "It should be faded out so you almost can't see it -- you'll just seem more toned than usual." Excited to try it? Read on for body contouring tips so you can get started today.

Start with an all-over tan
Think of this step like prepping the canvas. "First, self-tan your whole body, and wait for the color to develop. Then, shower to rinse off the excess," say Vezirian. "You need to start with a nice, even base color before you contour." If you plan to contour with self-tanner, Vezirian suggests using the same formula in the same color you used for your all-over tan. "You may be tempted to go darker, but don't," she explains. "Layering the self-tanner is what creates the contour."

You may not want to contour your abs, legs, and arms. "For certain areas -- like the triceps -- you need to have some definition to begin with," explains sunless-tanning expert Judy Lee. If you have a fuller figure, she suggests sticking with the sides of the thighs and the bottom of the stomach. (Keep clicking for how-to tips for each area.)

Whatever you do, don't draw on a 6-pack and expect it to look natural. "You want to do the bottom of the tummy, stopping at the belly button," says Vezirian. "Your stomach will look flatter and more defined." However, the sides of the abs should be left to a professional -- or an extremely advanced self-tanner -- because it's difficult to do right.

To create the contour, simply layer on more self-tanner or apply body bronzer.

Legs are the easiest body part to contour because you have a good amount of surface area to work with. Contouring the thighs is also great because it can disguise cellulite and stretch marks.

"Start with the sides of the thighs -- the area you see in the mirror when you turn to the side," says Lee. "And apply self-tanner in long, even strokes."

You may also want to apply self-tanner where your butt meats your legs, blending downward. "This creates a shadow to make the behind look more lifted," says Vezirian.

Arm contouring is subtle, but it can definitely help define the muscle you have. "Use your fingers to draw the self-tanner right on the line of the muscle," says Vezirian. She suggests contouring the tops of the collar bones and decolletage, as well.