Pet rats can be great but it can be a pain to clean their cage at times. Litter training them makes it so much easier and cleaner. Having to dump out the entire bottom of the cage out and put new litter in makes it very expensive, time consuming, and a big hassle. The first thing you need to do to train your rats is to get a litter box (smallish in size). A ferret size corner one works well, as does small kitten litter pans. Now before you put this litter box in their cage observe your rats. They will probably have one area in the cage where they use the bathroom the most. Put the litter box in this spot. Now if you were using litter in the bottom of their cage and are now switching to using a litter box you should use the same litter that you were using to fill the litter box. This will make them more likely to use the litter box. If you have just gotten your rats and want to start them out with litter training them you should use any of the high quality litters that are out there. For example, I like to use Yesterdays News but I have also used Carefresh in the past as well and it works fine but is a little more expensive in my experience. Next on your way to litter training your rats is to pick up any stray poops that are around the cage throughout the next week, or however long it takes your rats to get the hang of it, and put them into the litter box. This way the rats make the connection between using the bathroom and the litter box. Every time you empty the litter box to clean it you should save a little bit of the old litter to put on top of the new litter. This helps the rats continue to smell that that is their litter box that they should be using the bathroom in. The rats that I've had have taken to litter training very quickly, it only took a few days. Females usually take to litter training more easily than do male rats so keep that in mind. Have fun with your pet rats!