The basic idea is to get the king out of the center with your pieces (like all of the basic mates in endgames), and the opponent's king is going to try and go to the opposite color of the bishop you have, and you try to get them on the same color bishop you have to be able to checkmate.
http://en.wikipedia.org/wiki/Bishop_and_knight_checkmate
http://www.chessvideos.tv/forum/viewtopic.php?f=12&t=802
I can't do this mate! I was just now playing against much lower rated opponent than me, and he ended up trading his last piece for my last pawn. In silman's endgame course silman says that it's so rare that there's no point in studying it but it's now happened twice so I think it would be worth the time to know how to win these. Can someone explain the technique?