According to this 7Days article, Westerners are better tippers that Arabs. It doesn't seem like it's based on any factual or statistical evidence, but one thing I agree with is that no rules are set in the UAE about tipping, and this can lead to some confusion.
In general, I prefer to tip rather than not tip. And while the below is just an idea of what I feel are right amounts to tip, I may be wrong, so feel free to give your own assessment about tipping.
1) Taxi drivers: I tend to round up the fare, or give an extra 5 dhs (in Dubai). In Abu Dhabi, I round up the fare or give an extra dirham or two. Except if the driver is rude, like the one time the driver screamed at me for getting slightly lost. Then I don't tip at all!
2) Waiters/waitresses: If there's a 15% service charge included on the bill, then I usually don't tip. If there isn't, I give a 15% tip.
3) Food delivery people: depending on the size of the order, anywhere between 5 and 10 dirhams.
4) Hairdresser: I tip the hairdresser (anywhere between 10 to 30 dirhams, depending on whether it's just a blow-dry, a cut, or highlights) and the person who washed my hair (5 dirhams).
5) Nail technician/masseuse: 10 dirhams each.
6) Car cleaning/car drying men at the carwash: 10 to 20 dirhams, depending on how many there are.
7) Person doing repairs at the house: Dhs 10 (varies, depending on the extent of the repairs)
8) Person carrying your groceries to the car: 3 to 5 dirhams, depending on the amount of change I have.
9) Cleaning lady: 10 Dirhams for 2 hours of work.
10) Bartender: I usually don't tip....which is weird because in Canada I'd always leave a dollar per drink. Should I be tipping the bartender?
I can't think of anyone else that I usually tip...I must have forgotten someone. Any thoughts?