Depends on how big the hole is PP, if it's fist sized, go to lowes, get some dry wall compound you use to fill cracks, and some mesh that sticks to the wall, and go at it, or if you have some drywall laying around, cut out a square in the wall, then on the other sheet, cut out a square thats 3 inchs bigger all the way around, then cut that extra 3 inchs off, but leave the paper, and use that paper, and some drywall compound to adhear it to the wall, and sand it down gently, and put some more compound on the wall.
I have learned how to use the mesh/compound very well over my teenage years.
Heres a search on DIY Network, some good info there.
drywall repair Search Results : DIY