Originally posted by irontigran 1...Nf6 is statistically better and more flexible, but 1...d5 is much better for beginners.
I'm assuming some d5 variation like the Slav and Semi-Slav are statistically as good or better than Nf6 openings though, but I agree that it's a nice, flexible opening move.
After 1. d4 always reply 1. ...Nf6 and if White then plays 2. c4, then 2. ...Ng8. If White then plays 3. e4, reply 3. ...Nf6 or even 3. ...Nc6. White is lost as he has filled the center with pawns that can be easily attacked.
Only move your horses no matter what White plays and you will ensure that you have created no exploitable pawn weaknesses. Never move a pawn during the entire game at all. This is a hypermodernism at its best.