I turn 5 times a day, its easy because I am home on the farm all the time - I have an alarm set on my cell phone for five points evenly spaced throughout the day, first one at 7am and last one at 8pm. I've read that the minimum for hand turning is 3 times, but that a mother hen will turn the eggs up to 90(!) times a day. That said, the only time I've had embryos stick to the side of the egg and die is under a (first timer) broody hen. For the sake of full disclosure, we have three incubators running, the first one is a Genesis whatever-number-has-the-fan, with am auto turner that the eggs are in for the first (most critical) 7 days. Every Monday when we set new eggs, we move the 7-day eggs to the still air Little Giant (ultracheapo model) and begin hand turning. At 18 days they go into the Hatcher, which is another cheapo LG, but worls fine and I like that I only have to clean one base (hatching is messy).
Turning an odd number of times per day is best, as they dont end up spending all night sitting on one side - it alternates from day to day. If they sit every night on the same side, they're more likely to stick and have issues. What I do to tell one side from another is write the date (in pencil) on the side of the egg when I collect it, and which hen if I catch her 'in the act', then when I set them I write the date set on the blunt end of the egg, so I can tell which hatch is which. Turning is done so that dates are either up or down, and while turning 60+ eggs by hand does take a while the first few times, eventually your hands get used to the motion and you get faster - it usually takes me 3 minutes or so to turn 60+ eggs in the LG as well as however many we have stacked on top of the turner in the Genesis.
Hope that helps some.
