You're full of excitement, you've got the cash ready and you've decided to take the leap.
Hold on for just one minute! I've come up with a short list of things to consider when getting your very own fish tank.
Things to consider:

1. How much room you have for your aquarium tank.
   
2. Is there an electrical outlet positioned near the preferred spot of the aquarium.
   
3. Start with small to medium sized aquariums (10-20 gallons) if you're just starting out (see below for a chart of the common aquarium tank sizes and weights).
   This is so you save a little bit of cash and gain a little more experience before venturing into bigger aquariums.
   
4. Aquariums come in a variety of shapes and sizes.
   The most common one of course is the long rectangular shaped aquarium tank.
   Octagon, hexagons, cube and cylindrical tanks are also popular.
   Choose one that best suits the room where it will be placed.
   Remember, the aquarium automatically becomes "the" attention grabber and is usually the first thing a person sees when entering the room.
   
5. Glass or acrylic (plexiglass).
   These are basically the two types of building materials used for making a fish tank.
   Both have its pros and cons, but my suggestion is to choose one made up of glass if its your first aquarium.
   Glass is durable, cheap and very scratch resistant.
   

Below is a chart of the most common aquarium sizes and weights to help you choose: *take note of the filled weight, as this is critical for choosing an aquarium stand.
Small Aquariums Size | LxWxH | Filled Weights 2 1/2 gallon | 12"x6"x8" | 27lbs 5 gallon | 16"x8"x10" | 62lbs 10 gallon Leader | 20"x10"x12" | 111lbs 15 gallon | 24"x12"x12" | 170lbs 15 gallon High | 20"x10"x18" | 170lbs Mid-sized Aquariums Size | LxWxH | Filled Weights 20 gallon High | 24"x12"x16" | 225lbs 20 gallon Long | 30"x12"x12" | 225lbs 25 gallon | 24"x12"x20" | 282lbs 29 gallon | 30"x12"x18" | 330lbs 30 gallon Breeder | 36"x18"x12" | 348lbs 40 gallon Breeder | 36"x18"x16" | 458lbs 40 gallon Long | 48"x12"x16" | 455lbs **High, Long and Breeder are just terms to differentiate aquariums that have the same volume but have different dimensions.
That's basically it.
Make sure you go through each consideration on the list carefully so when you actually do purchase your fish tank you'll have no regrets.