It starts with an awkward moment.

A business transaction happens, and it's hard to know what to do next -- is a thank you enough? A handshake? Or is it a good time to slip somebody a few bills?

It depends on the service provided. While a waiter might be obvious, not all situations are as clear-cut.

"The reason why we tip is to show respect to the service provider," said Diane Gottsman, an etiquette expert. "Part of our responsibility is to be a respectful community member and give to those who deserve a tip, without going overboard."

She suggested that a good rule of thumb is "when in doubt, do."

Here are a few people who may not first come to mind when considering gratuity.

1. The exterminator

There are generally two types of exterminators: those who do monthly maintenance visits, and those who treat a specific infestation. Exterminators in the latter category are usually tipped, said Timothy Wong, the director of M&M Pest Control in New York City.

On average, 20%-25% of customers tip, Wong said, in an amount ranging from $10-$20. "There are exceptions. Some will tip $40-$50," he said. Some clients give up to $100 if it's a big job, like sealing a building against vermin, which can take up to three days to complete.

Wong said there's a clear tipping correlation between those who don't have infestations, and those who do. Those with happier results are more inclined to tip.

"They will hug you, tip you, feed you, you name it," he said.

2. The cable guy

The worker who comes to your home to install your cable may work for the cable company directly, or might be an outside contractor. A tip for good service is often appreciated.

"If he's out there in the hot sun, maybe digging around under your house, you want to show him a gesture of kindness," said Gottsman.

Some large providers -- like Comcast -- have policies in place that prohibit workers from accepting tips.

But that doesn't mean they won't. It doesn't necessarily have to be a cash tip, Gottsman said. It could be a cold glass of water or lunch, especially if the job takes several hours.

Wyatt Carpenter, a technician in Canton, Ohio, said people tip him, especially on extreme weather days. This past winter, he said he worked in temperatures as low as minus 20 degrees.

"It's not life-changing money," he said of his tips. "Five, 10, 20 bucks...."

Another cable technician, Christopher McBriar, said while he doesn't expect a tip, it's nice to get $10, which he will use for lunch that day.

A nonmonetary tip he appreciates: When a customer is prepared for his visit. "They have moved the furniture away from the wall or unpacked the TV from the box ... that goes a long way too," he said.

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3. The spray tanner

Adding on gratuity for a hair stylist is fairly typical, but tipping for beauty services doesn't end there.

"Makeup and tanning is so overlooked," said Suzie Basset, a full-service salon owner in San Antonio, Tex. "That's part of the grey area because [customers] just don't know." She said clients will occasionally ask her if a gratuity is expected.

"It's uncomfortable for you, the payer, and it's uncomfortable for me, the receiver, on how to handle that," she said.

A safe bet is to tip salon service providers anywhere between 15%-20%. It is sometimes assumed that if the service provider is the salon owner a tip does not have to be included. Basset said that's changing, and many owners now welcome gratuities.

4. The dry cleaner

The person behind the counter of your local dry cleaner may not be the same person actually doing the work of removing the stain from your shirt, but a small token of gratitude wouldn't go amiss.

"If someone got a stain out of my favorite white dress, I would ask them, 'Can I leave a tip? What would be a great way to say thank you?'" said Lizzie Post, the co-author of Emily Post's Etiquette, 18th Edition.

It doesn't have to be cash. The Yelp Gratuitous Guide to Tipping suggests some flowers or a bottle of wine. That may sound romantic, but, "if they remove a wine stain from your favorite Marc Jacobs dress," it might be worth it.

5. The road service employee

Maybe it's a flat on a busy highway far from home, or a dead car battery on a stormy night. A panicked moment, made manageable by the tow truck guy who came to the rescue.

"Yes, he's working, that's his job, he is getting paid a salary... but maybe he's on a busy highway, or came in the rain in the middle of the night," said Gottsman. "You can offer it."