A couple of years ago we bought a cheap incubator on ebay. It has a thermostat and automatic egg turning - which are pretty vital if you don't want to be a complete slave to your eggs. The one we have will hold up to nine eggs.
When collecting the eggs to be incubated make sure they are clean - only use a damp cloth to wipe them if they are dirty. Washed eggs will require more humidity so the ideal is to pick only clean ones. Keep them pointy end down in a cool place - like a pantry not a refrigerator! Rotate them daily. They will be fine to keep for up to 10 days before incubating, but the success rate will start to diminish after a week. Don't write on the eggs.
The incubator needs to be scrupulously cleaned before use and turned on a day before setting the eggs. The eggs should be placed either on their sides or pointy end down so that the oxygen in the air cell in the non-pointy end is accessible to the growing chick.
Our incubator needs about 100ml of water in the base to give the appropriate humidity and the thermostat is set at 37.5 degrees Celsius. It should be placed in a spot where there is little likelihood of temperature extremes or draughts. Ours is set up in a corner of the kitchen where it won't be forgotten and the kids can watch the eggs hatch while eating their dinner.
As long as the water level is maintained there is little to do for the first seventeen days. Beware of power cuts but the eggs will hatch if the temperature drops for a few hours. A shorting vaporiser left our latest batch in the cold for four hours - but eggs still hatched.
On the seventeenth day the humidity needs to rise so I add up to 200ml of water to the base of the incubator. I also take out the egg roller and the top shelf so that when the chicks hatch they find walking easier.
Once the eggs start to hatch I leave the chicks in for a few hours to dry and fluff out before transferring them to our homemade brooder box. Some chicks find it hard to walk at first but most will come good after a day or so.