To train a rabbit well, you must be willing to spend some time every day doing nothing but watching the rabbit and acting only on the behavior that needs to change. Only when the rabbit is fairly reliable can you begin giving it time outside its cage (home) when you aren't watching like a hawk.
There are two steps in training rabbits not to chew and dig. These apply to any behavioral training except for:
The steps in training a rabbit are:
Example: Bunny is chewing on furniture
Sometimes, you can give rabbits pieces of the thing they want to chew: their own bit of carpet, for example, providing they aren't ingesting it. This is especially useful when the attraction is the particular consistency (nothing pulls quite like the threads from a piece of carpet).
Warning: Ingestion of non-natural fibers can be deadly! A few bits aren't likely to hurt, but if a fair amount is consumed, it can block the rabbit's stomach to the point that it loses interest in eating. Enzymes will not break up a major blockage of such fiber; surgery is the only option.
For digging, build a "tunnel" (top isn't needed, just bottom, high sides, and end. Cover the bottom with a bit of carpet or something similar. Bunnies LOVE to dig at the end of tunnels. (Same thing can be accomplished by putting a board with carpet tacked on between two pieces of heavy furniture against the wall...just be sure the board can't move or the bun will be digging the carpet beneath where the board was meant to be.
Finally, if the rabbit insists on chewing YOUR carpet, even if he has his own piece (or whatever behavior you're trying to stop), use the "No!' and put him in his cage for three minutes or so. (Ignore his angry shaking of the cage bars.) Let him out after a few minutes (but not until he is no longer shaking his bars), and repeat the procedure, if necessary. If you have to do it a third time, leave him in his cage until the next period he would normally have out.
(Loss of freedom is the severest of punishments--remember this when you want to hold a bunny that wants down.)