Opening preparation - Sokolsky/Polish opening
The move b2b4 as first move is not seen very often in chessgames, but some amateur players always play it with white. I will show you one line for black that you can play against the Sokolsky/Polish, called the Outflank variation.
It is not a refutation of 1.b4, but it can give black decent play.
In that line there is one trick you should know. I've mentioned it in a sideline variation in the following annotated game :
http://www.chessgames.com/perl/chess.pl?yearcomp=exactly&pid=43488&eco=A00&title=Sokolsky+Plays+1+b4 (Sokolsky playing 1.b4 himself)
http://www.chessgames.com/perl/chesscollection?cid=1028768 (Game collection with 1.b4)