You will want it to be the focal point of the room, so choose a site where the tank is stable, out of direct sunlight, and safely out of danger of being jostled or cracked. Don't purchase a small tank, thinking that you will learn with it and later work your way up' to a larger tank. Smaller tanks are harder to keep stable than large tanks and you can't keep as many fish in a small tank. A 10 gallon tank will only comfortably, and safely, house a few fish. That is only a temporary situation, and not one you should try to duplicate in a home aquarium.
Mechanical filtration is necessary to remove debris and gases from the water.
There are many types of filters on the market. Ask the store personnel to help you choose the right system for your tank. Biological filtration, which occurs when the tank has cycled', consists of healthy bacteria that consume the harmful bacteria found in the water. You can purchase test kits at any pet store to monitor the ammonia, nitrite and nitrate levels. If you intend to keep tropical fish, purchase a safe heater designed to heat a tank the size you plan to set up.