Facebook is still the top social networking site, and if you are a band, it's a smart move to have a Facebook Page. Making some grand statement about how having that Page doesn't matter is a disservice to the local bands that are out there working their tails off for a craft they can only hope to make into something lucrative. Not everyone can be the next Gin Blossoms or Kongos, but exposure and support everywhere you can doesn't hurt.
We all know the basic rules for Twitter. Even if you are new to the social media site, there is still a basic etiquette. Don't post 100 times a day, post meaningful content, engage and interact with other users. Don't spam, don't beg for follows, etc. etc. Unless you are a teen girl obsessed with her favorite band on Twitter. Then all of the "normal" rules go right out the window.