Know that sometimes things aren't what they seem. If you are using a dubious peer-to-peer network a file labelled as music could be something else completely. It could be something malicious. See if there are any reviews or comments on the torrent before downloading. It'll help you make the best decision.
Don't download music illegally. Instead, purchase CDs and load them onto your computer. In this way, you support your favorite singers and musicians. This way, you can have access to the tracks and add them to your mp3 folder without risking breaking the law. And the best part is that your home CD collection will be awesome.
If your taste in music changes a lot, consider using a site that allows you to stream music, rather than download it. Streaming allows you to listen to a large variety of songs, but the music never resides on your computer. This can save you money and space on your hard drive, so it is sometimes the better option.
While free music downloading sites should be avoided, there are free streaming sites that allow you to build playlists. As for downloading music, avoid any site that has not been established for a significant amount of time, whether paid or free. Go with one you know you can trust so that you can be rest assured your music will always be available to you.
Check the file size on any MP3 you are downloading. It's easy to mistakenly download something you had no intention of downloading. This may be extremely dangerous for your computer. Be sure the size of the file is as you intended for it to be. Any file that's really large or kind of small needs to be deleted before you open it.
If you really love an artist, check out their website for music. Most bands maintain an online presence where they offer information on music and tours, and they will sometimes offer free music there. This might include otherwise unreleased tracks or a song off of a new album they are trying to promote.