All of the suggestions above are also what I typically use, except I also try to have at least 1 or 2 instrumental songs along with vocals, just to break things up. Also, I try to identify whether a song is 'up' or 'down', i.e. I wouldn't want an album with 12 'murdered my girlfriend' songs, if you see my point. Balance in all aspects is good. Good luck on your project! -btmp