The most important thing to start with is to set our aquarium in the right place. You should keep it out of the direct sunlight, in a peaceful corner of the room, so that people moving around it wouldn't scare the inhabitants. Of course there are many fish that look astonishing when they are in the direct sunlight, but when the tank is close to the window the possibility of algae growth rises.
For beginners there is a strict advice not to buy any tanks lesser than 60 liters! The smaller ones are harder to keep in stability, and are not suitable for many species of aquarium fish. Of course if we want to own bigger and territorial fish that may be aggressive (such as most cichlids for example) the tank must be bigger.
There are several types of aquarium filters you can choose from, all of which need to be cleaned on regular bases, with the “living” water from the tank, so that the bacteria living inside the filter do not perish, putting us back to the beginning, risking the life and health of our fish. From my experience the most practical and efficient type of filter is the external canister filter, which are a little more expensive, but you don’t have to clean them that often, and due to the size of their exterior, they provide the biggest setting for the nitrobacter. A canister filter is irreplaceable in larger tanks, but it is always good to have a back-up filter in case something goes wrong.