The best method I've found is to use a tubberware type tub that will fit into the tank the fish are in now as well as the one they'll be moving into. Fill the tub with water in the tank, shoo the fish into the tub (easiest if there aren't any decoration in the tank). Then you just carry that up to the new tank, submerge it, and let the fish swim out.
A large bag will work as well, but is harder to work with since it wil tend to collapse on itself. Either way, you don't end up chasing the fish around, it doesn't get removed from the water, and you don't worry about it getting stuck in the net.
Good luck!