If you can get a copy of Storey's Guide to Raising Ducks, there is a chapter on ducklings that is immensely helpful.
Use the search on this site - we have discussed temperatures (90F the first week, dropping about 5 degrees a week after that, always give them warmer and cooler areas anyway, and watch for hyperactivity or lethargy and adjust the temperature). Water deep enough to dip their bills and wash their eyes, but not so deep they can get soaked and chilled.
Water is one of the most important things to manage - they need it to drink and wash 24/7 until at least six weeks of age. And they splash. So, set something up to confine their splash. Again, many good ideas here, with pictures and everything!
We debate about feed regularly - find recommendations that make sense to you. Medicated chick feed not recommended, but some say amprolium is okay. There is a sticky about treats that is really good.
Ducklings can get into trouble - faster than you could imagine, and sometimes the most bizarre "accidents" happen. One person had pictures of one of her ducklings stuck inside the plastic bottle she used as a waterer. Their feet get caught, their necks get caught, they fall into things, eat strings, knock things over, try to squeeze into too-small nooks, you name it. They panic, and don't always use good judgment.
Keep them from drafts, big feet, other pets, unsupervised little kids, falling, poisons, bits of metal and sharp objects. Watch their poop. If it's bloody or unusual for ducklings, call the vet. If they are listless, or don't eat, or throw up alot, call the vet.
They quickly grow from tiny to much bigger, and are fairly high maintenance until, I'd say, about ten weeks of age. It is not their fault, by the way. It takes some patience and time to manage them. With eleven runners in the house for three months, I had no unpleasant smells, no disasters. It was a little work, but I now have ten (yes, we lost one at about seven months of age to either something toxic or an internal health issue) healthy, wonderful ducks that are easy to manage, have great personalities, and produce abundant, delicious eggs. They eat slugs and weeds and make fertilizer.
