+1 for demos. Demos help a lot. A lot more than just playing pcw.
The matches (pcw, pracc, cups, etc) helps a lot too, but you don't really learn so much from them as you do from pros' pov demos. Also watching your own demos from matches is very good. You see the mistakes you made and then you fix them or do them different way.
I don't recommend csdm that much. I had times when I played it like no tomorrow and noticed that it doesn't help a shit. You don't learn to shoot by playing csdm since the situations in matches are totally different. If you overplay csdm it will only affect negatively to your gameplay. Just play it enough to keep your aim in shape.
50 % pcw, 40 % PoVs, 10 % csdm = success.
2012-06-02 12:44:48