1. e4 Nc6 2. d4 what do I do

I like playing responding to e4 with Nc6 but I don't know what to do about 2. d4. should I stop playing this move or is there a good response?

I'm not looking for a full on opening just a good follow up move and the idea behind it

2..e5 is played by some, but 2...d5! is better.

thanks I'll try those

Your options are e5 (Kevitz defence/Dark Knight System) with possible Scotch transposition after Nf3 and d5 (Nimzowitsch Defence) which tends to lead to French defence style positions, another option would be d6 with a Dark Knight Pirc. Might I recommend buying either the Dark Knight System or 1... Nc6 as they would both improve your understanding of said position and its possibilities 

I thought the 3...f6 lines were considered better? 

Yes, wasnt intending to be facetious, I just thought he had recommended them due to an issue with the Bf5 line, I have only played the d5 system a few times and Bf5 felt comfortable, having skirted over the f6 lines they felt cumbersome in comparison but indeed first impressions can lead one to the wrong path. I was always slightly afraid of the Nc3, dxe lines, in the same way I am afraid of playing f5 vs Nf3

e4 Nc6 d4 d5 e5, Bf5 before f7-f6 is logical, for it blocks white from playing Bd3 for free.

As for e4 Nc6 d4 d5 Nc3, in addition to de4, black also has the Reefschlager French option, 3...e6, which of course is not the most aggressive way to play the French, but it is solid and playable.