First, some background: Lash extensions are natural or synthetic fibers that are glued on top of natural lashes. A lash extension technician might attach one fiber per natural lash or cluster a few fibers on each lash, depending on the look you're trying to achieve. The extensions are secured close to the lash line with a tiny drop of adhesive.

Eyelash extension fibers are composed of synthetic or natural materials. Synthetic lash extensions are made of a very flexible plastic that mimics the fine, soft texture of human eyelashes. Natural lash extension fibers may be made of silk, animal fur (mink and fox fur are popular) and even human hair.

Lash extension fibers vary in thickness, length and curl type, which allows stylists to build a wide variety of looks. "Most women want full, natural, classic lashes," says Lindsay Terrill, aesthetician, master lash artist and owner of Flutter & Wink Beauty Boutique in Vancouver, Washington. Others go for more fashion-forward or glamorous looks, like ombre extensions (black at the roots with colorful tips) and Russian volume lashes, which are created by attaching multiple fibers to each natural lash.

Image via @sugarlashpro

To make sure you're getting the best eyelash extensions, it's important to see a certified stylist. Terrill is a certified Xtreme Lashes technician who has been doing lash extensions for five years. She also has plenty of happy, gorgeous customers, so I figured I was in good hands.

To find an experienced stylist, start at the website of a reputable lash extension brand. Companies like NovaLash, Sugarlash and Xtreme offer online tools to help you locate certified technicians in your area. Terrill suggests cross-referencing the names of any stylists you find with feedback from online review sites. "Yelp reviews are great to check," she says.

Terrill recommends asking lash stylists a few questions before booking your appointment, including whether she is certified, trained and state-licensed; how many years she's been doing extensions; and whether or not the glues she uses contain formaldehyde. (The response to the latter should be a definite "no.") Also ask how long it takes her to apply a full set of lash extensions. "If they are new, and it takes them less than two hours," Terrill says, "that may indicate improper training, which could lead to an improper application."

The cost of eyelash extensions varies wildly depending on where you get your extensions, what type of extensions you get, and who's doing the service.

"Pricing for a full set will range from about $125 to $300 depending on experience, location, et cetera," says Terrill. "Generally, lower prices would indicate a new stylist or an untrained stylist."

Salons usually break down the cost of a full set of extensions by the number of lashes that are applied (for instance, 85 per eye) or the amount of time the stylist spends on your service. The material of the extension also dictates cost. (Natural fibers are more expensive than synthetic.) These rules also apply for touch-ups, which might cost from $50 to $150 or more.

How long your eyelash extensions last depends largely on how well you care for them. With proper care, your lash extensions will look great for three to four weeks. (For tips on after-care, click to the next slide.)

However, even the best lash extensions don't last forever, and you'll see them fall out with your natural lashes; losing one or two every day is normal. Your lash extensions may cling on for weeks or months, but they'll probably start to look patchy after four or five weeks. To keep your lash extensions looking full and even, get touch-ups every two to four weeks.

Lash extension maintenance can be a bit tedious, but proper care is essential to making your investment last. After-care instructions may vary depending on your technician, extension material and extension brand, but most experts agree on these guidelines:

1. Steer clear of greasy products, which break down lash extension glue. "Keep oils, lotions, and creams away from the eye area," says Terrill. "Makeup remover must be oil-free and water-based."

2. Don't use cotton pads or swabs for eye makeup removal.The cotton fibers can get caught on lash extensions. Terrill suggests using disposable makeup sponges.

3. Avoid wetting your lash extensions for 24 to 48 hours after application. Eyelash extensions can and should get wet, but the glue usually needs a day or two to set, depending on manufacturer's instructions.

4. Keep them clean. Full disclosure: In five years of wearing extensions, I never washed them with anything but water. However, many lash extension experts recommend washing them with a gentle, oil-free cleanser. I tried and liked Xtreme Lashes by Jo Mousselli Eye Makeup Remover & Facial Cleanser, $15, at Terrill's recommendation.

5. Avoid unnecessary pressure. That includes rubbing with a towel or smushing your face in a pillow -- side sleepers, take note.

6. Brush them daily. Lash extensions get tangled and tweaked, so use a spoolie to fluff and comb them in the morning. 7. Minimize time spent in steam, chlorinated water or saltwater. Shower with your bathroom door open and skip the steam room. If you love to swim, wear goggles or rinse your lashes with fresh water afterward.