How do bands usually divvy up money between members?

The thread about how The Verve got a fat chubby in the pooper on the Bittersweet Symphony deal and speculating about how much Richard Ashcroft would be worth if he'd gotten the royalties from that song, got me wondering about how that usually works.

Do bands usually split the royalties from a song equally? Do the royalties instead go the guy(s) who wrote the song? Or does this vary from band to band? If it varies from band to band, I feel like this could get messy. When forming a band, I can't imagine the first thing you do is draw up a contractual arrangement for future monies.

So how does this usually work? Educate me.