That best way to start a band imo is to just start messing around with a group of friends. It may be a good idea to start off with cover songs or something simple until the band has a good idea of its sound and abilities, but I wouldn't go more than a couple months before starting an origional set. And I'm sure you already know this, but if not the best thing for a band is individual practice outside the regular sessions. Either the members improve on their own or you're going to suck collectively.