Ah the joys of rats, they are actually my favourite animal due to their intelligence, loyalty and trainability.
I've only owned two and due to the short life span (2-4 years) I'm never going to get another fancy rat again, however I will be getting two Gambian Pouched rats in the future (African breed, size of a cat, 8 years average life span).
My quick notes would be you need to have at least two of the same sex (preferably from the same litter, but introducing is easy) as they are social animals. Even in the short time my eldest was in his cage he did need another rat to keep him company (he even slept in my bed, the cage was just used to get water, food and toilet).
Cleaning the cage once or twice a week is vital, you can train them to use a corner litter tray:
1. Remove old shavings, disinfect cage and replace with new shavings.
2. Place an old sheet over the floor with shavings under - still comfortable.
3. Get a corner liitter tray, put in cat litter and put a few bits of shit in, this will make it the only place smelling of toilet.
4. Replace rats, every time they do not shit in the litter tray just put the shit in there - they soon learn.
5. Once the rest of the cage is clean for over two days with no accidents, then remove the sheet.
Once that's done you can just have a litter tray out of the cage - so when roaming round the house they know where to go, just don't move it once they get familiar with where it is. If you do then you need to release them next to it, they'll remember.
Also lots of toys, tubes and things to climb - intelligence means they need stimulants. Make sure they're big enough though.
Always have dried food available in their cage, but a few bits of fresh fruit and veg are good once or twice a day.
They love to chew apple bark, good for teeth.
Only bad points of owning rats = short life span, very susceptible to tumours and bad press - easy to convert friends though.