We employ local guides who greatly appreciate recognition of services rendered. Tipping about 5 USD per day (if you are happy with the service) is appropriate, but not compulsory. For drivers who render services for several days in a row, 3 USD per day is appropriate. Remember, a tip is not compulsory and you should feel free to tip according to your own beliefs.
At small restaurants you may want to round up to the nearest 1USD. At upscale restaurants, a tip of 10% is appreciated but do note that restaurants often levy a 10% service charge on the bill.