I do what Naker suggested, looking at their recent games and seeing what offensive and defensive tactics they use.
but I also try to do this when I've got a big match or i'm feeling hardworking (or very bored!)
1. I check if the player's active (conference info) If he's inactive, chances are its gonna be the same tactics he played last game
2. I use the ratings for his team in the games as a ROUGH estimate for what to play against him
Eg if he has strong ID but awful OD, perhaps you could go motion / run and gun...
3. I look at past games and try to estimate his team's enthu
4. I check his players gameshape
5. I check out their roster to compare my wages vs theirs and which positions the opponent has higher waged players at
(if genearally I have players with higher salary I go Man to Man)
its all judgement calls and a bit of luck really... but yea.. at least this gives me a rough idea of what to expect / play
hope its helpful :P