good responses to 1. Nf3 So I am a decent player, rated by my estimate at around 1000, even though my actual rating is 5 years and thousands of games out of date. In playing the chess engine in chess free on android, I quickly stopped playing 1. e4 because the center counter/scandinavian became very annoying. I switched to d4, and later to nf3 so that people playing against me wouldn't know how to react (most are sub 1000). I, however, don't know myself what the best response is. The two main lines are 1. Nf3 d5 and 1. Nf3 Nf6. I think that I prefer Nf6 for black, but how should I continue from there? Of course, it depends on what my opponent does, but what should be a position I aim for with black?
Until you reach 14-1500 strength, opening theory is not very important. 
One of the best coaches in the world for beginners, National Master Dan Heisman, said:


  It does not matter who gets the advantage out of the opening if one of
  the players is likely to lose a piece to a simple tactic in the
  middlegame. Losing a piece from an advantageous position will almost
  always result in a lost position. So study tactics, not openings,
  until you almost never lose pieces to simple tactical motifs.


However it is good to know the ideas behind opening moves, such as controlling the center, developing, etc.

So 1...Nf6 and 1...d5 are both good moves. They both control the d5 and e4 squares and aid development.