Cleanliness is incredibly important.
You must clean and sanitize all of your equipment right before you start brewing, and keep everything clean throughout the process. Bacteria and fungi are everywhere and if enough of them get into your beer they will completely ruin it. The good part is that if you do clean everything you will make an excellent first batch of beer. Later stages will also require you to clean and sanitize other items, and when we say that you should refer to the following cleaning and sanitizing instructions. Cleaning refers to the removal of any visible crud, sediment, film, dust, etc.