Well, I have 2 types of incubator. One is the R-Com 20 from Brinsea. It is digital and automated and I just have to dial in the humidity I want and leave it and it will keep it rock steady as long as I keep the water tank filled.
My still-air LG is more difficult. I usually add extra sponges into the bottom to hold more water, and I plug at least one of the 2 air vents, but sometimes that means I have to nudge the temp down slightly (very slightly) because the one less air vent means that the temp goes up a bit. Oh, I also have a digital thermometer/hygrometer in it to show me the temperature and humidity level.