Since that wildly successful 1980 Calvin Klein ad campaign, the American public has changed its perception of denim —once the uniform of the young and working class, jeans are now a staple in the wardrobe of virtually every American, regardless of age or socio-economic status.

Buying jeans is not as easy as it once was. There are endless varieties, styles and brands, and the cost is rising as fast as the cost of gas.

Nowadays, denim is an investment. One of the questions I’m most frequently asked by my clients is how to find jeans that fit well and look great. Buying denim is complicated, so read on to demystify the process.

How to find the right fit

Start by asking how much the jeans will shrink or stretch. When I buy 7 for All Mankind jeans, I choose one size smaller because I know they stretch. Most people don’t clean denim after each wear, so factor that into the stretch equation. Look at the fabric label: are they 10 percent cotton, or a cotton, polyurethane or lycra blend? If they contain two percent stretchable fabric, they will give more than 100 percent cotton, but even 100 percent cotton stretches after a few hours.

Ask the sales associate about their return policy. You may want to leave the tags on and wear them for several hours — at home please to avoid a Minnie Pearl look — to know if they fit. Fit is crucial in the hips, the rise and the length.

To determine if you want a straight leg or a boot-cut, decide what type of shoe you’ll wear with the jeans and how they look on your body. If your hips are wide, choose a boot-cut: the flare at the bottom will balance your hips and create a slimmer look. If you plan to wear boots with the jeans tucked inside, choose a straight leg. A boot-cut will have too much material to tuck inside a boot; they are designed to wear over, not inside, boots.

If you have narrow hips, either style will look great. If you have wide hips, avoid back pockets. If you can’t find jeans without back pockets, keep embellishments to a minimum. The more attention you draw to your booty, the larger it looks. If you have great hips, embellishments like multi-colored stitching, crystals, studs or beading will draw attention to your cute behind.

If you have a short upper body, choose low-rise jeans to visually elongate your torso. If your upper body is long, a high-rise jean will make your legs seem longer, and you’ll look taller.

The length of your jeans should cover almost the entire heel of your shoe. If you plan to wear your jeans with stilettos or boots, you probably won’t be able to wear them with flats. The difference in the hem length can be two to five inches, depending on the height of your heel.

How to care for your new jeans

It’s important to decide how you will clean your jeans. Will you dry clean or machine wash them? It will determine how much they shrink and fade. Begin by reading the manufacturer’s care label. It is usually best to follow those instructions. If you want them dry cleaned, make sure you tell the cleaners; otherwise, they may wash your jeans. Never alter denim until it has been washed or dry cleaned.

If your denim has expensive embellishments like crystals, studs or beads, dry cleaning may be necessary to avoid damaging those details. Ditto if they’re black to avoid fading. If you launder them yourself, turn them inside out and use cold water on the delicate cycle with gentle detergent. After I launder my jeans, I remove them immediately, shake them, line up the seams, and hang them from a shower rod to dry. If they have stretched, I dry them with medium heat for about 10 minutes before I hang them to finish drying.

If you still have trouble finding jeans, take an objective friend shopping. Insist they be honest. After all, you don’t want anything to come between you and your jeans.