Everyone likes buying jeans. But how do you know what looks good?

Professor Leonard Bess of the Fashion Institute of Technology (www.fitnyc.edu) knows all about how to fit women in the right pair of jeans, and recently he shared his tips at a talk on the Rutgers New Brunswick campus.

Bess told students that jeans fashion is based entirely on optical illusion. Knowing which tricks bring which effects is the key to picking out the jeans that best suit your body.

“What I like to call ‘jeanetics’ is the most important part of choosing clothing,” he said. “If you don’t know who you are, you don’t know what to wear.”

It begins, he said, with being honest about your body type.

Rectangulars have shoulders and hips of near equal width and a poorly defined waist. Bess recommends butt-hugging jeans, relaxed fits, and flare or boot-cut legs — they give you curves. Baggy and skinny leg pants are out.

Pear-shapes have a defined waist, rounded hips, and a small bust. To show off your legs, Bess says, go for boot-cut, low-rise pants. Choose dark washes. Do not choose pocketless pants or tight fits.

Hourglasses are the classic figure, with a defined waist and even shoulders and hips. They can wear almost any style that has an excellent fit, though Bess suggests boot-cut and slight flare for the best look. Stay away from bagginess. Designer jeans are perfect.

Inverted triangles have broader shoulders and narrow hips. Boot-cut, flare pants and high rise are for you, Bess says. Back pocket embellishment is a plus. Straight fits, dark washes and the no-pockets look are all minuses.

Rounded types have wide ribs and a full waist. In order to elongate the torso and minimize the hips, Bess says to try boot cuts, relaxed fits, and dark washes. But no capris, baggies, or high rises.

Diamonds have small shoulders, broad hips, and slender legs. They are one of the hardest types to fit. Bess recommends relaxed styling, stretch denim, dark washes, and low-rise. Avoid capris, high rise, and rear embellishment.

“All garments make some kind of illusion,” Bess reminded the audience. “The trick is finding the right one.”

By NJ My Way contributor Elyse Dempsey-Arner