Daily and Weekly Tasks
Daily Tasks
Check Water
Give them their food in evening as this is when they are more active (and more in morning if you need to top it up). If they are excreting a lot you're probably feeding them too much!
Keep an eye on the health of your Rats - just make sure there isn't any changes in behaviour or physical appearance.
Make sure room isn't too hot or cold! Don't want them to be ill!
Weekly Tasks
Full Cage Clean-out - when you clean the rats out it can be easier if they aren't running about so either put them in a smaller cage or in a high sided box (open of course!) and keep an eye on them.