Most people never have a problem and don't waterproof their floor. But, if you're using Ditra, you could get some KerdiBand and go around the edges, but there's still the problem with the doorway...if you contain any (large) spills in the room, they'll still go out the door. You'd also have to band any seams in the Ditra. Waterproofing up the tub skirt is problematic, too although you could caulk there. If you're worried about it getting beneath the tile around the flange, you could use some KerdiFix to seal around that area between the DItra and the flange.
If the toilet leaks, it probably wasn't installed properly. When reinstalling the toilet, ensure it doesn't rock (shim if it does BEFORE resetting and installing the wax ring), and then tighten down. Unless you regularly have water fights in that room, generally, don't worry.