Kastin is quick to point out that there are exceptions to every rule, and some women in their 40s can look fantastic with long hair, like Demi Moore here. But for most mature women, long hair "does tend to drag one down and generally make one look older," Kastin says.

The key is to pay attention to your face shape and hair texture. If your hair is super healthy and your face is on the round side, you can give long hair a whirl. But if your face is long or your hair is either really thick or really fine, it's best to try one of the styles on the next slide.

Sure, it may seem like only "older women" go for short haircuts, but it's worth trying. If longer hair drags your facial features down, going shorter can be like a mini-face lift. The key is to stay away from stereotypical "mom" or "old lady" cuts and stick with something fresh and modern, like Halle Berry's choppy pixie.

Technically this is a good rule for any woman, not just those over 40. Kastin says to "make sure you get a haircut that you can make look good at home." The reasoning is pretty simple: If your haircut involves complicated and time-consuming styling, you probably won't do it most days, which means your hair is going to look less than stellar.

So if you're a whiz with a flat iron and have time to kill, go ahead and get an asymmetrical pixie like Jenna Elfman's. But if you don't know a round from a paddle brush, stick to one of the cuts on the next slide.

A simple cut with a few layers is almost fool-proof. It requires very little styling -- just a quick blow dry and maybe a curling or flat iron if you want to look extra polished.

But the real lesson here is to get a haircut that works with your hair texture and lifestyle. It's crucial to talk with your stylist about your styling abilities before he starts to cut so you can help him determine what type of style will be ideal for your hair. A good stylist should give you a realistic idea of the amount of effort a particular cut will require. That way, you'll have a fighting chance at looking (almost) as good as you do when you walk out of the salon when you style your own hair.

There's a saying that goes something like this: "If you're old enough to have worn the trend the first time around, you shouldn't wear it the second." Side braids and high ponytails sometimes work (exhibit A: Christina Applegate's perky pony), but other times can make you look like you're reliving your glory days. After all, we wore almost the exact styles back when we were also wearing unitards and big, teased bangs in the '80s, so now it's time to leave them to the tween set. If you go for these looks despite our advice, you're going to look like you're trying too hard, says Naeemah Carre, stylist at Blow, the New York Blow Dry Bar.

Remember that it's OK to be in your 40s, and you're not fooling anyone trying to relive your cheerleading days with your hairstyle. You're way better off trying a style that's more "grown up."