We hate to get preachy on you, but if you want your skin to look great well into your 80s, you'll follow this advice, courtesy of Audrey Kunin, M.D., founder of DERMADoctor; David Bank, M.D. author of "Beautiful Skin: Every Woman's Guide to Looking Her Best at Any Age" and Olga Lorencin, owner of Kinara Skin Care Clinic in Beverly Hills, Calif. When asked what the worst possible things for our skin are, these topped their lists. So now, repeat after us, "thou shalt not" ...

"If you wont quit for your heart and lungs, quit for the sake of vanity," says Bank. When you smoke, you diminish the skin's ability to get the oxygen it needs. Without optimal oxygen, skin cells can't renew themselves. "It accelerates the wrinkling process by damaging the skin and impeding the repair of your skin," adds Bank. So in addition to the obvious vertical lines and wrinkles around the mouth, your skin overall will look lackluster and dull.

"Don't do tanning beds, period, end of discussion," says Kunin, explaining that every young melanoma patient she treats has used tanning beds. Ten minutes in a tanning bed is equal to getting a full day of unprotected sun exposure -- yikes! So instead of baking on your color, Kunin recommends "applying color" by way of self-tanner or bronzer. Our readers love Jergens Natural Glow Express, $7.49 and Banana Boat Summer Color Sunless Tanning Lotion, $7.69. Need help perfecting the application process? Check out this how-to video.

"Incidental sun exposure (the little bits of sun we get) while walking, driving, etc., build up over the years," says Bank. He recommends applying SPF 15 daily. If you plan on getting more sun exposure, wear SPF 30 and reapply every two hours. See the sunscreens our readers love and hate here. "And don't be fooled into thinking that your clothing acts as sun protection," says Kunin, adding that our clothes only provide an SPF 4. Protecting your skin from the sun daily will help prevent premature aging (think brown spots and fine lines) and skin cancer. One other bit of wisdom: "protect your eyes with real UVA and UVB sunglasses," says Kunin. "The sun can cause cataracts, blindness and even melanoma."

"At night is when all of your skin rejuvenation happens," says Lorencin. If you wear makeup to bed your skin can't get the oxygen it needs. When skin is suffocated, "your natural collagen building process is compromised," she says. Kunin adds, "it will also clog pores and act as food for bacteria," which can cause breakouts and make pores more visible. In addition, if you don't wash your face at night, you're not doing anything to fight aging, combat pimples or treat other skin issues since you're not exfoliating or adding beneficial spot treatments or moisturizers.

Check out some of our readers' favorite makeup removers here.