What should i use as floor lining in a rats cage?

Hi, im not to sure about her to set up a rats cage, so wondered if you could all help, if you could give a full idea of how to set up a cage, then please do but the main thing i want to know is what do i line the floor of the cage with if not wood chips, i have heard you use fleece, i have some to use but would prefer if they didn't chew it and need me to buy more... also, when it comes to bedding, what do i use for that as well? Is fleece a good idea again, but should i litter train them first before i use that? Thanks!!!!