actually very few people remove fish, uproot plants and dig around alot to gravel vacuum. most people just use the gravel vacuum to remove the water for their water change.
this is what i do:
1) put the gravel vacuum into the water
2) starting with the end that is attached to the gravel vac, slowly put the siphon tube into the water but keep the other end above the water line (like putting a straw in a drink)
3) at the end of step two, there should be almost no air bubbles in the siphon tube
4) cover the end of the tube with your thumb
5) lower the tube into your water change bucket and then release your thumb
6) you should now have water flowing from your tank into the bucket
7) hold the gravel vacuum in one hand and slowly move it around the tank
8) don't disturb your plants' roots, just focus on cleaning the open spaces
9) if you really want to clean a specific spot, shove the end of the gravel vac into the substrate and watch the dirt go!
10) remove only about 10% to 30% of your water
11) stop the end of the siphon tube with your thumb again
12) with your thumb tight on the end of the tube, lift it straight up into the air over your tank
13) release your thumb
14) remove the gravel vacuum from the tank and go dump out your water