They are very similar to chicken eggs, with some key differences:
1. They take 28 days to hatch (for mallard derivatives--35 days for muscovies)
2. They need a very high humidity at hatching time
Other than that, there is some disagreement about what else should be done differently. Some people incubate at a higher humidity throughout (but I find a higher humidity means drowned ducklings at the end due to inadequate air cell development--it all depends on your ambient conditions), others spritz the eggs with water throughout (I don't but probably should), some people claim ducks should be incubated on their sides and turned by hand (I don't and personally don't think it makes a difference, but others disagree).
Many people say ducks are harder to hatch than chickens. I've not had much trouble--I consistently get 85-90% hatches. But I've never tried to hatch chickens (actually, I hatched a small batch of bantams last year, quite successfully--but it's not enough to compare accurately). I do know that quail are easier than ducks--they just pop right out, right on time, at 90-100%.
Hope that helps! Good luck.