When it comes to travel to the United States, one of the most confounding cultural differences is tipping. While it may seem like an unusual practice to Australians, rest assured it does serve a purpose in the States.

Normally reserved for the service industry, tipping is not only a way to show gratitude for a job well done, but it also supplements fairly low wages in job fields where tipping is factored into annual salaries. While leaving a tip is never required, it is considered very rude if you don't.

To take some of the mystery out of who and what, here's a quick guide on tipping in the US.
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Taxis And Drivers

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If you're headed to the 'Big Smoke' (any sizable US city), chances are you're going to take a taxi or have a driver at some point on your journey. Even if it's just a shuttle from the airport to your hotel, it's customary to tip your driver.

10 to 15 per cent of your total fare is the norm for taxis or limos. If your driver assists with your bags, you can throw in a couple extra bucks if you want to. For shuttles (free or otherwise), tip two to three dollars per person.

Don't forget to tip your driver. (Image: Getty)

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Hotels

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When it comes to tipping at a hotel, there are a few people that you should keep in mind. A bit tricker than other situations, tipping amounts will depend on the calibre of the hotel, how long your stay is and what you have in your wallet. To avoid any embarrassing faux pas, it's best to keep a stash of smaller bills on hand.

• Bellstaff/Porters: One to two dollars per bag is appropriate. If you have a lot of bags or they're heavy, you may want to consider upping it to five dollars.
• Cleaning Staff: If you're staying two days or more, leaving one to five dollars per night is the norm. You can leave it on a table or nightstand each morning, or in one lump sum on the day of check-out.
• Room Service: 10 to 15 per cent of your total bill.
• Concierge: Tips are determined by the difficulty of each task. For simple requests, leave two to five dollars. For more complicated requests such as last minute dinner reservations at the hottest restaurant or sold out tickets to that new show, consider tipping around 20 dollars. For more involved planning, or seemingly impossible tasks, consider tipping anything upwards of 20 dollars.
• Valet Parking Attendants: One to five dollars each time the attendant brings your car around.
• Doorman: While it's not necessary to tip the doorman every time you see him, if he goes out of his way to secure a cab for you or help out in some way, slip him a few bucks to show your appreciation.

Tip during your hotel stay for the best service. (Image: Getty)

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Restaurants

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When you're going to a restaurant you should always leave a tip. Usually you'll only need to worry about the wait staff, though if you want to use a 20 as subtle bribery to get a better table, the hosts or hostesses are normally happy to accommodate you if they can.

Generally speaking,15 to 20 per cent of your total bill is the standard for groups of four or less. 25 per cent of your total bill for groups of five or more. Note that some restaurants will add a mandatory gratuity to the final bill for especially large groups.

15 per cent of your final bill is the norm for restaurants. (Image: Getty)

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Bar Tenders

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If you're planning on spending any time in the clubs and bars while living it up in the US, keep in mind that bar tenders do expect a tip for their services.  Why else would they be doing all of those fancy moves with their cocktail shakers?

Just leave one to two dollars per drink on the counter. If you're sitting at a table, the same rules apply to the wait staff bringing the rounds.

Don't skip the tip when you're having a drink. (Image: Getty)

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Curbside Check-In

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Curbside check-in isn't always available, but when it is, it can be a God send. If you're running a little behind, or the check-in lines at the airport are just too long to handle, simply sidle up to one of these kiosks in front of the airport to check-in. Some curbside check-ins will charge a small fee for baggage handling. Otherwise they are free to use. Of course, if you're checking bags, tipping is very much appreciated.

Two to five dollars per bag handed to the attendant will ensure your bags are processed efficiently.  If you have heavier bags, opt for the larger end of the scale. Keep in mind that these curbside check-ins are often cash-only.

The convenience of curbside check-in is often worth the tip. (Image: Getty)

The above guide should cover most situations that travellers find themselves in when heading stateside; though, if you run into unfamiliar territory, it's best to tip. And, if ever in doubt about how much, 15 per cent is a safe estimate.