I bought one of the kits at the lfs
with a 25-foot hose that attaches to a faucet just like the things used to fill water beds. It has the wide tube at the other end to vacuum the gravel with a removable slotted cover to prevent sucking up fry, shrimp or anything else that could get pulled into the tube.
When you turn the water on it creates a siphon and you remove as much water (along with the sediment or other nasties) as you want to replace. When you reach that point, pull the tube from the water and let the siphon empty the hose. To fill the tank you move a piece at the faucet end and the water is directed to the tank. I get my water from a well, so no chlorine issues. I take a half-gallon glass jar and add some water to mix the aquarium salt in, disolve the salt completely and pour it into the tank separately.