Make sure the cage is kept above ground and away from drafts. If you use a big multi story ferret cage you do not have to have it above ground because the rats can climb to the top lookout if they need to.

For toys I use the following:

Solid running wheels (Quality cage company or Wodent Wheels)
Hammocks lines with fleece
Snuggle pouches (these hang from the cage and are sort of like hammocks)
PVC pipes
parrot toys
soft cat balls
parrot ropes for climbing
cardboard boxes
wooden chew blocks

Do not use:
wire wheels
toxic branches
toys that contain wire


You also need to invest in ceramic food dishes and water bottles. Glass water bottles are recommended because they cannot be chewed. Lixit makes water bottles that attach to the outside of the cage but have the spout sticking into the cages so the rats cannot chew on it.