I would recommend playing d5 and follow up with e6 and simple development like Nf6, Be7, and castles. This is called the queen's gambit declined if white plays 1. d4 d5 2.c4
Here's an interesting article: http://www.jeremysilman.com/chess_instrctn_bgnrs/120603_crt_easy_op_rep_bk.html
This link is a bit more specific.
http://en.wikipedia.org/wiki/Queen's_Gambit_Declined
I am having some serious trouble defending against the 1. d4 opening move.
I have been playing a friend in real one on one chess for some time now. He always plays as white and I always play as black. Just recently he has started playing 1. d4 vice 1. e4. I am fairly comfortable defending the 1 e4 position but do not have a clue how to defend against the d4. To be honest, i don't know if there is a name for this or how to look up tips on it on the internet.
If anyone can help out or give some tips I would really appreciate it!