Now, the first step on your "to do" list is two fold; choosing where to place the aquarium, and picking out a tank.
About Choosing an Aquarium Location
It is a giant pain to move a fully set up aquarium, even a few inches. Once your aquarium is set in place, it is highly unlikely you will be be moving it, so placement considerations are very important. Measure areas that will allow for the tank. Keep in mind that you will need sufficient space or access around the tank for cleaning/maintenance, and don't forget to take into consideration where your electrical outlets are. Make sure to pick a spot where direct sunlight will not shine on it, especially in the hot summer months. You will probably want to place the tank where it can be easily seen and enjoyed from the sitting areas in the room. A number of people make their aquarium the primary focal point of the living room, and the television secondary. Some people are concerned about the effect the weight of a tank and water will have on the floor structure in the room. Even a 55 gallon tank weighs about the same as two adult men, so if you don't feel comfortable with two of your heftier friends standing next to each other in the middle of your living room floor, place the tank against a "bearing wall" (usually an outer wall). That's the strongest part of the floor.
When choosing your tank location, also keep in mind that your going to have to be able to have easy access to the tank, both from above (for maintenance) and below, if you are going to have a sump or storage there.
Some people install their tanks "inside" the wall. Impressive, but make sure that you really want to make the long term commitment before you start making structural changes to your home. Now, if you are in the process of building your own home, an in-wall set up is something to consider and can easily be incorporated into the house blue prints before construction, rather than having to tear a wall out after the house is built. If you are renting your home, check with your landlord before spending any money on an aquarium set up. We had a "no pets in the house" clause in our lease, so for many years we couldn't have a tank inside, but our landlord did give us permission to keep 2,500 gallons in various systems outside.
The decision on where the aquarium is going to be placed often goes hand-in-hand with what size tank you will buy, because of the available space you may or may not have.