once the new tank is set up and ready for the fish, take the fish and put them in a 5 gallon bucket with water from the current tank. use enough water so it is 4-5" deeper than they are tall.
then every 5-10 minutes add about 1/4 - 1/3 gallon of the new aquarium water to the bucket. once it gets almost full, remove half the water from the bucket, and then refill it in the same manner. once the bucket is about full again, net the fish and put them in the new tank.
this depends on the size of the fish and the bucket, but you get the picture. just slowly mix the waters from each tank until it is primarily water from the new tank.
this reduces the stress/shock on the fish. i acclimate all my fish this way and it works very well. obviously if its a small fish from a LFS and a small bag they come in, i don't use nearly as much water. but i have never had any problems.
also, as with any new fish in an aquarium, you will probably want to add some stress coat to the new tank once they are in
good luck!