There are a variety of siphons available. I bought a 5 gallon bucket from Big Al's online, too, so I know its clean and never been used for anything else. For my small tanks, I use a smaller bucket I have. To replace the water in the smaller tanks, I use a clean, previously unused, plastic disposable cup. To replace the water in the larger tanks, I fill the bucket and use a 2 quart clean, previously unused pitcher to dip into the bucket and pour into the tank. Never use anything that has been used for something else - anything you use in an aquarium should be clean and free of all chemicals and/or detergent residue and should only be used for the aquariums.
Use either something like Python or a regular siphon tube. If your tank is small a regular siphon tube would suffice. If you go to any fish store, they should have some kind of siphon tube - regular ones are very cheap. Once you have it, you siphon the water out from the bottom of your tank. This way you vacuum the gravel and remove uneaten food and fish wastes from there.
LOL, yup Just siphon the water (using the siphon tube) into the bucket and then pour the water from the bucket into the sink. Or, if your siphon tube's hose is long enough, you can siphon the water out of your tank directly to the sink. Only remember that if your tank is sitting below the level of your sink, it won't work.