Just off the top of my head (please read that link!!)
Brooder - safe place, no dogs, cats, clumsy humans, things that can fall over or catch fire, brooder needs to be warm enough (generally, 90F the first week, dropping 5 degrees a week until they are at room temperature). Watering station that will provide water and will not soak the brooder quickly. Look around the forum to see ideas... This will matter more than you may imagine. Do this right, and you will not be regretting your decision, or facing eviction, within three days!!!! Brooder needs to be where there is fresh warm air, no drafts. No chance for ducklings to fall or get stuck. Preferably where you can hear them. Don't ignore sounds of distress. Check on them every time.
Water - need it 24/7 for probably ten weeks. Clean & refresh as many times a day as you can stand it (thinking at least 3 at first)
Food - if chick starter, nonmedicated (unless you are okay with amprolium, that is a personal choice), with extra niacin from capsule or a sprinkle of brewer's yeast on each bowl of food.
Bedding - several choices, but make sure they don't eat it!!!! Give it the sniff test before you use it. If it is dusty, get them out of the brooder while you clean and fix up the bedding. Must be no-skid, to avoid splay leg.
Have on hand antibiotic ointment, bandages, vitamins-electrolytes-probiotics. Search the forum to see more details.
If you make changes, hang around for at least 20 minutes after to make sure the ducklings won't get themselves into trouble with the changes. (new waterer, bedding, rearranging things)
Now your turn . . . what do you have ready? Is the brooder all set up and ready to go? All supplies near at hand? Do you have a thermometer so you can be sure the brooder is warm enough? Who is your backup if you cannot be there?