When to tip and how much to give causes anxiety for many Angie's List members. "I'm not always sure who to tip, especially those that provide a service at my home," says Angie's List member Shelia Sewell of McDonough, Ga.

Nearly 70 percent responding to a recent online poll say they tip to show appreciation while more than a third tip at least 20 percent. "Why do I feel compelled to tip just about everyone?" asks member Deborah Pursifull of Snoqualmie, Wash.

Others are more selective about who they choose to reward. "I don't think tips are always called for, like with a plumber or electrician," says member Nina Rankin of Pittsburgh.

In addition to members, we reached out to several highly rated service companies to get their view on gratuities. Across the board, they say they don't take it for granted and equally appreciate a positive review or recommendation. "Sometimes, referrals from family, friends and co-workers are the greatest tip of all," says Jennifer Miller, co-owner of A Do Hair Design, a highly rated Indianapolis hair salon.

Here are the top 10 Angie's List categories - determined by poll respondents - in which members most often consider leaving a tip:

Movers

Doing the heavy lifting may not require a bonus. "We never expect or ask for a tip," says Mike Atkinson, owner of highly rated Experienced Movers in Pearl, Miss. "We don't want to burden our customers with trying to figure in a tip after we've given them an estimate on the cost of the move."

However, grateful homeowners tend to show their appreciation, regardless. For light moves, offer a $10 to $20 tip per mover. For larger moves, companies say a tip of $20 to $50 is appropriate.

House cleaners

"If customers ask me about tipping, I tell them that it's never required, but would always be appreciated," says Linda Rabenberg, owner of highly rated Linda Rombach Personalized Cleaning in St. Charles, Mo. "We don't expect tips because I pay my employees well and house cleaning is fairly expensive to begin with.

"Almost all our customers leave a Christmas tip or gift," she adds, which might be a box of chocolates or 100 percent of their pay. "During the rest of the year, very few customers tip."

Contractors

If you use a handyman or lawn care professional regularly, give them a $15 to $50 tip once a year - perhaps during the holidays - as a thoughtful "thank you."

Contractors, such as plumbers and electricians, don't expect a tip. However, some Angie's List members feel compelled to reward those who go above and beyond. "I have tipped my plumber," says Friday Hamlet of Box Elder, S.D. "He went out of his way to help me by driving to my home to hook up the water so I could wash clothes. All free of charge!"

Pet sitters/pooper scoopers

Pet sitters and pooper scoopers don't require a tip, but they say it's appreciated. "I've had people give me gift cards for fuel or coffee," says Jim Skirvin, owner of highly rated K-9 Scooper in Fairfield, Ohio. "I certainly don't ask for anything extra, but it's nice." If you regularly use the same one, provide an occasional 15 percent tip or annual gift.

Hair stylists/barbers

Deciding who to tip at salons confounds even the best of us. "Many guests have questions regarding how to tip when there is more than one person helping out," Miller says. "If someone other than the stylist shampoos your hair, that person will always be appreciative of a little extra money."

Stylists say they typically receive a 15 to 20 percent tip, but it varies. "There are clients who always tip and clients who never tip," says Karla Watson, owner of highly rated Flip Hair Salon in Portland, Ore. "Clients shouldn't worry about tipping a certain percentage, but should tip the amount they feel comfortable with."

Taxi/shuttle/limousine

When hiring a bus or limousine service, be sure to check that company's policy on gratuity. Some strictly forbid it, while others build it into the rental price. "We operate under different rules than most transportation outfits," says Kay Smith, manager of highly rated Caledonian Coach Co. in Stafford, Texas, which provides private bus charters and tours. "It varies per region." Typically, the driver receives at least $1 per passenger.

It's customary to tip taxi drivers 15 to 20 percent. If you don't have cash, make sure the driver accepts credit cards.

Manicurists/pedicurists

Most times, the same nail technician will do both your manicure and pedicure and a tip of 10 to 20 percent is appropriate. However, if different people perform individual services, then be sure to split the tip accordingly. "I'd say 95 percent of clients leave a tip," says Laura Puhl, owner of highly rated The Laura Gregory Salon in Columbus, Ohio. "If you can't, you can't - it varies. Some people tip way too much."

Car wash

A full-service car wash - which may include vacuuming, waxing and towel drying - should warrant a $2 to $3 tip for a car, or $3 to $5 for an SUV, truck or van. Many places post a box for tips near the exit, with all tips split between the workers. If there's no box, give a couple bucks to whoever performed final touches after the wash.

For full detailing, consider a 15 percent tip. "I try not to place any expectations on gratuity," says Kenny Ryan, owner of highly-rated Echelon Detailing in Carrollton, Texas. "The services we offer are pretty well covered in the cost. When it does come, it's a bonus."

Massage therapists

Massage therapists at spas often receive a tip of 15 to 20 percent. "It varies from place to place, but most massage therapists work on commission as an employee of the salon or spa," Puhl says of her Columbus salon. "Any extra reward is always appreciated." However, a medical or rehabilitative massage typically doesn't call for gratuities.

Animal grooming

Customers find pet groomers in a variety of settings - from big box stores to mobile grooming vans. If you're especially pleased, tip 15 percent of the bill or $2 per dog. Be sure to offer a little extra for a filthy Fido. "People will leave a larger tip if their dog is difficult," says Jennifer Lavelle, owner of highly rated Kool Dogs Training Academy & Kool Klips Grooming in Brookhaven, Pa. "But I always tell them it doesn't matter if they tip me or not."