I don't know why no one has answered you before now,surely someone knows more than I, but I'll try.
I remember clearly that chicken eggs take 21 days to hatch but don't remember the exact temp that is best. I know birds have a higher metabalism than humans and therefore higher temps, but hens can be away from the nest getting food and water for a while without damage to the embryos.
I've heard of teenagers hatching eggs by tapeing them to their bodies so my guess is around 85-90 degrees F.
Good luck!

I'll ask my daughter because she has eggs going ALL the time. I did learn that it's difficult to mix egg types in the incubator because of the size -- larger ones are closer to the heat source, etc.

Here's a pretty good guide.

Here is a link that might be useful: Egg incubation

I have one of the marketed foam hatchers also, purchased in a local farm supply store. You want to set up and test run your hatcher for 101 degrees F, +_ 1 degree with water in the trench/pan supplied. Mine came with a clear plastic tray for the purpose, and normally filling it once was enough with one slight refill before the 21 days for chickens was complete. Haven't tried ducklings yet. I did the X & O thing on the eggs in pencil. Two or three times a day, every five or six hours I faithfully rotated my eggs by hand. I averaged a 55% hatching rate using whatever eggs I found from my hens while doing nothing special. Others tell me vitamins for the hens and rooster could improve the hatching rate. One thing is for sure, you need to clean things up real good after each batch to prevent problems in the hatcher.

It is also a good idea to seek out web groups that focus on your selected kind of birds for advice and such. I like the MSN groups, and have a website I manage, but it is about No-till gardening/farming. I belong to two other groups that are centered on chickens. One is managed from the UK.

Your incubator should have two spots for water in the bottom fill the outer one with water, insert turner and regulate to 99.6, (this can take some time), after you get it regulated add your eggs. After 18 days (for chickens) remove the turner and fill the other spot with water ( make sure the first spot still has water also). Chickens can hatch anywhere from 19 days to 23 but the strongest seem to hatch out 20-22 days. I run 4 incubators at a time when I hatch little ones. Also it will do better if you leave a few spots empty. I think mine holds 42 when full but I normally only put in around 35.

Good luck with your babies.

The correct temperature is 101 F. for a "still air" hatch. That means there is no fan to circulate the air. If it has a fan then WECAREAGAIN is correct. HOWEVER, the wafers are not always as good as they should be, so it's a good idea to watch carefully. A good one will not allow the temp to vary more than 1/2 degree F. That is close tolerance, but sure makes a difference in your percentages. I always got better hatches when I turned them myself than with the auto turner. My theory is that part of the reason a hen turns them is to give them exercise and the turner is just too slow and easy. After awhile I quit worrying about x and o markings and just reached in with damp hands and rolled them around a bit...I figured if the hen could do without marking the eggs so could I. ;O)