"When people are too aggressive with their skin, do too much exfoliating and too many peels, that's when skin becomes sensitive," says Zdenka Sutton, a facialist at Le Posh Salon in Los Angeles.

Overdoing it with any scrub can be bad, but the ones with ground-up nutshells in particular are hard on your skin, says esthetician Kate Somerville, founder of Kate Somerville The Clinic in Los Angeles and the Kate Somerville product line. "These nuts are pretty jagged and can actually cause tiny tears on the surface of your skin," she says. "Those tears will then appear as sensitivity or irritation, and may also serve as little reservoirs for bacteria to attach and thrive."

Sutton says your best bet is to use a gentle scrub or peel at home every two to three weeks and to always hydrate your skin after, just like facialists do at the spa.

"Don't do it!" Somerville says. Even if it seems safe, trying any new procedure before a big event is just asking for redness, breakouts, and possibly even hives. Her advice: "Test a new product three to four weeks before something important. That way there's time for your skin to calm down." And if you're lying on the facialist's table and she suggests a peel or new treatment, speak up if you've got a special occasion coming so she doesn't take the risk.

Sure, with some products (lipstick, eyeshadow, hairspray) you can tell pretty quickly if it's working for you. But skin care takes time, so instant gratification isn't really an option. "Your skin cells renew once a month, or every 40 days if you're 40, so it takes time when switching skin care gears," King says. "To see results, work with one [product] range you believe in consistently, using it morning and night for six to eight weeks."

Of course, sticking with one regimen for two months and still not liking the results would be a major letdown. So seek out professional help (whether from a dermatologist or esthetician) before you stock up on serums. True, an appointment with a pro might be a bit pricey, but as King points out, it's better than wasting money on products that won't work for you.

What you shouldn't do? Simply ask your friend with clear skin what she uses. "You're not the same as your friend, so you won't necessarily have the same reaction," King says.

Somerville adds that there are an "infinite number of skin types and combinations -- and everyone is different." So a professional can help you sort all that out and choose products that will really help your skin. However, King adds, "if you feel like you're just being sold something and the salesperson hasn't addressed your skin concerns, then don't take [those recommendations]" and try someone else.

The opposite of the try it and leave it type? Those of us who hold on to products way longer than we should. Any product with a use-by date should definitely be tossed once that day passes, King says, but even products without official expiration dates can go bad. "Emulsifiers go bad � gel or cream-based products need to be used quickly," she says.

Not convinced? "You're keeping [products] in a hot, steamy bathroom, it's an environment that's inviting for bacteria," King says. "And jars that you put your hands in mean bacteria is getting in, not to mention the fecal bacteria that's in all bathrooms." All in all, it's pretty gross, so you want to toss your products after five or six months -- before they turn into bacteria-riddled messes and start causing breakouts and who knows what else.

In a perfect world none of us would pick at our skin, and Sutton highly recommends avoiding it, since it can cause scarring. But in the real world, estheticians know that people are popping pimples at home. Their beef: We're doing it all wrong.

Using dirty fingernails, squeezing too hard or incorrectly, or popping a zit that's not ready to be popped can lead to bruising, scarring, infections, and yep, more breakouts, Somerville says. So if you can't resist attacking that whitehead on your chin, watch this video to see how to pop a pimple the right way. Because as King says, "acne isn't permanent, but scarring is."