I might start playing the semi-slav. Ok I will have to learn how to play against the exchange. What is the best move order? ok 

d4 d5 c4 c6
d4 d5 c4 e6

then lets take it a step futher

d4 d5 c4 c6 nf3 e6 (or nf6)
d4 d5 c4 e6 nc3 e6 (or nf6)

What if white plays pxp on move 3? is it really bad or does it just transpose, or can black take advantage of it? Thanks.

Ok I have to learn the positions, but going into the opening any of the above ways, is there some advantage to one move order over another? Is there something I want to avoid cause it is tough for black? Oh i want something where the positions has some fight in it.

I was looking at a post before, and it was saying the new Kaufman book makes a reconmendation for the move order, but why?

Thanks.