Make sure she's fed well, her water bottle is always full and her enclosure is cleaned regularily....basically anything you'd do for any rat really....just more so with a female nursing a litter. As the pinks become pups in about 15 or so days their eyes will open and they'll start to follow her to her food and water sources. Usually by day 20 they are eating and drinking independent of their mother but will still nurse from her until they are weaned.

Female rats move their young all the time, it's their instincts at work. With larger litters an experienced female rat will often break them into smaller groups, move from group to group nursing them and then pile them up back together on and off for face and butt washing.