Done it dozens of times. Do yourself a favor and purchase two new hold down bolts and nuts. Most old ones are rotten. Also, spend a few extra bucks and get the wax gasket with the rubber flange built into it. Once the water supply line is shut off, flush the toilet. Then, get a two gallon bucket, and pour it directly into the bowl. This should do a good job of siphoning out any residual water in the bowl.
Remove your supply like from the tank, not from the valve on the wall. Take off the two nuts on the hold down bolts, and pull the tank. Reinstall the wax gasket, and two new bolts, and install the toilet back on the flange. Sit on the toilet to get a good, solid seal, using a slight rocking motion. Tighten the new bolts, but not too tight, because they can break the porcelain if tightened too much. Cut off the excess length off the bolts, cap them, reinstall the water line, and you're done!