Well, the poop should be hard...if it's soft and squished into blankets and such, you should check their diet to make sure they don't have diarrhea (avoid watery foods, etc.). I always do a full wipe-down of the cage and play area every morning with fragrance-free baby wipes. I remove their little poops at this time, and shake out their blankets. (I replace blankets every two to three days, depending on how dirty they've been with their food and urine.) My boys are litterbox trained, so it's always been pretty easy to get the poop out of their cage every day. If you haven't litterbox trained your rats yet, you definitely should! It makes daily wipedowns much faster.
ETA: Aside from the daily morning wipedowns, I also do a full cleaning of their cage once a week, in which I remove all the shelves and wash them fully in the bathtub, and wipe down their cage wires, and completely wash their playpen floor--all with with antibacterial soap and warm water.