Fischer Describes His Fischer Random Chess Rules (audio; bobby-fischer.net):
Fischer Random is a version of chess that I developed, or invented you could say, where you shuffle the back row of the pieces, not the Pawns. The Pawns stay the same on the second rank of each player. You shuffle the back row of the pieces and each side has the identical shuffle so everything is symmetrical just like in the old chess.
There are just a couple of rules. One Rook has to be to the left of the King; one Rook has to be to the right of the King; one Bishop has to be on a light colored square; and one on a dark colored square -- for each side. That's basically it.
When you castle, we don't say you're castling Kingside or Queenside. We use algebraic notation: we say you're castling a-side or h-side. Now when you castle h-side, that's like short castling. When you castle a-side, that's like long castling. Now it doesn't matter where the King and the Rook start out; after you castle you castle into the standard castling position.
It's very simple. You can learn the rules in about two minutes.
When it came to chess, Fischer usually knew what he was talking about.