1. It is not a good idea to wash your filter media with regular tap water. The tap water can kill the beneficial bacteria that is built up in the filter. Use distilled water to clean out your filter and its components.
2. You should always thoroughly research the type of aquarium you are going to be setting up before you purchase it. Make sure you have the proper gallon capacity and shape that will fit in your home.
3. You should always research the different types of fish you are going to be housing together. Certain fish can be extremely aggressive and cannot be paired with other fish of different temperaments.