What is a good move for white if black declines the queen's gambit opening?

Question

What is a good move for white if black declines the queen's gambit opening?

Answer 1

Move your queen's knight to c3.

It's a good developing move and increases the pressure on d5.

Answer 2

There are many different declines.

1 d4 d5

2 c4 c3 or e3 or Nf6.  Heck, Nc6 is sort of playable.

In weird gambits I've seen 1d4 d5 c4 e5.  Technically that is QGD but just giving an all purpose move might miss the point.

Not knowing details and just guessing for an OK move, Nf3 or Nc3 would be good.

Answer 3

I assume by decline you mean 1.d4 d5 2.c4 e6.

In that case, you can play 3.Nc3 and after 3.Nf6 4.Bg5 Be7 5.e3 and such, it's just a normal Queen's gambit declined position. White will try to get e4 in as well and then black must exchange, giving white a (temporary) centre majority.

Exchanging on d5 is also playable. This can be done at any point, for example. 3.Nc3 Nf6 4.cxd5 exd5 5.Bg5 and really, if black plays out his Bc8 you're just going to disrupt his play with Qb3, attacking pawn b7 and d5. In this variation, you're just going for play on the queen's wing with the pawns. If you exchange all the pawns, black will be stuck with one (weak) pawn left on the queen's wing.  

Black can play differently, but either way you try to get e4 in, or you play the exchange variation and try to put pressure on the queen's wing. You can also play the exchange if black already played c6, in that case after cxd5 cxd5 you put your pieces (rook/queen) on the open c-file, which is mostly a bit better for white, who has a lead in development.

GL