I encountered 1. b4 recently as a surprise by a FM (he never played that before) and just played 1. ...Nf6 2. ...e6 3. ...d5. I think that's a fine way to get a decent position without having to know anything. Sometimes white is able to cramp black's queenside somehow, but the tempi he spends on that can be well-used by black to develop comfortably and set up kingside play (Bd6, Bb7 Nbd7 Ne4 and so on). I got a very good position pretty easily but messed it up in time trouble.
http://www.chessvideos.tv/chess-game...r.php?id=70789