Good advice alright but I have my own method which works quite well also I believe. For holes in stud partitions: pack the void with stout paper (cement sacks are ideal), roughen the edge of the plasterboard to give a key, prime with some watered down PVA and fill the void with gypsum bonding, leaving the surface slightly shallow. Bonding is great for these repairs and leaves a great substrate for "skimming". When dry finish off with gypsum skimcoat, sanding and painting to finish. This method works well most smaller holes up to 6" across. For bigger holes I would place a piece of plasterboard into the void, keeping it in place with some dry wall screws, then continue as above.