on 04/23/08 at 12:43:05:
if u want to avoid QGA and slav-semislav problems u could try 1.d4 d5 2.Nf3 Nf6 3.g3 and then c4. Only problem may 3...b5 but i don't think it will be played too often and it shouldn't be that problem anyway.
Can't Black play an early ...Bf5 and be fine here? For instance, 1.d4 d5 2.Nf3 Nf6 3.g3 c6 4.Bg2 Bf5. Probably Black could also play 3...Bf5 in this move order, since White hasn't played c2-c4 yet.
I also play the Catalan, but use it mostly as a substitute for the QGD, some lines of the Semi-Slav, and against the Nimzo move order. For instance:
1.d4 d5 2.c4 e6 3.Nf3 Nf6 4.g3;
1.d4 d5 2.c4 e6 3.Nf3 c6 4.Qc2 Nf6 5.g3;
1.d4 Nf6 2.c4 e6 3.g3, when there are some transpositional possibilities available into the Catalan, Benoni, English, etc.
"My" move order means that I still have to play against he Slav, QGA, etc. But I like this better than trying to play a set "system" no matter what Black does. If you want to maximize your chances of getting a real Catalan, probably 1.Nf3 and 2.c4 is the way to go, but you'll need to learn some English and Reti (which can be similar to Catalan) lines.