Well, what works the best is putting weight over the middle of the cage so that the floor slopes downwards. I usually get a plant stand and set it right over the hole with a nice big umbrella plant on it. Or arrange the plants to they slope the bottom of the cage. This only works if the whole bottom isn't resting on a table or something.
Hopefully that helps! I also like using shower curtains if you're having a problem with water spraying out of the cage, of running down the mesh and on the outside of the cage. You just tape it to the top and then tape it to the bottom (or tuck it under the cage and into the drainage pan, if you're using something like that), and the water should just run on the inside of the cage.
Hope that helps!