The general guidelines I was given was that if they've been vomiting for more than 6 hours or if they are vomiting and have diarrheoa as well to get them checked out.
The main issue, is of course dehydration. Extra drinks is good, and pedialyte can be good too, although some won't drink it. My girls LOVE it.
Keep an eye on wet nappies.
Mostly it's a hassle and you can end up with a lot of extra laundry. We had the vomiting and diarrheoa over the weekend. Ugh. Hope no one else in your family gets struck down.
Oh and the towel idea the pp suggested is absolutely the best thing you can do to make life easier at 2am.