This applies to all of my tanks -- I do 5 gallons for my 40, 65 and 75. Yes the 40 gets a larger percentage, but this is the easiest for me and keeps me a schedule. I have found that the easier it is to do a water change, the more apt one is to keep doing them.
Anyways, the night before (( sometimes this will happen days before hand if I get busy )) I will pour RO/DI water (( yes water needs to be first )) into a 5 gallon bucket. Plug in the powerhead and heater. At this point I will pour in (( slowly )) 2.5 Solo cups of salt.
The night of the water change I will test the salinity/SG and adjust if needed -- though have gotten pretty good at getting it right.
Test the salinity/SG of the tank's water -- in case I need to adjust the water change water.
Lay down an old beach towel to protect the carpet/bamboo floors from spills.
I will open the doors to the sump, and remove any excess algae from the sump --- both macro and nuisance.
Unplug skimmer, main pump, and powerheads.
Razor blade the glass -- front, back and sides.
Open up a little step ladder.
Put a different 5 gallon bucket on the ladder (( I use the same salt brand buckets, so I know that I am removing the same amount as I plan to put back in ))
Start the siphon and proceed to "gravel vac" the sandbed (( all of my tanks have shallow sandbeds )).
Keep doing this until I get all the sand and/or the bucket is full, which ever is first. If I finish the sandbed first I continue to remove water until the bucket is full.
Carefully carry the bucket to the powder room (( I really should put a lid on said bucket )), and dump it in the toilet. (( excess macro algae is placed in a plastic shopping bag and put in the trash )).
Collect the skimmer cup, acrylic panels (( there are next to the skimmer and helps control splashing from the sump )), sponge covers from the MP10's and from the Mag 5 return pumps.
Bring all of the above into the spare bedroom's full bath. Clean skimmer cup with an old toothbrush, rinse off acrylic and clean the sponges.
Rinse out the bucket.
Bring above items back to the tank that I am working on, and re-install
Carry fresh salt water to the tank and place it on the step ladder.
Hook up a hose to the powerhead that is in the bucket.
Plug in and let the tank refill.
Rinse out this bucket, and refill for next water change.
Turn on main pump, powerheads and skimmer.
Put away my water change items into a "supply" bucket.
Place bucket, ladder back into the water change closest in the half basement.
Clean the front glass from water spills.
Finally, relax on the couch and ice my back.
I believe that I covered everything, and if I still on schedule the above can be done in 30 minutes -- helps if I am listening to music.