Murder by numbers

I've just been involved in playing one of these murder games (you know, where everyone plays a part and the amusement value is largely determined by how willing you and your friends are to assume another persona and enter into the spirit of things. For a novelist and a people watcher it was just as entertaining watching the real reactions to people finding out they were serial adulterers, cheats, thieves, and murderers. Plenty of motive ;-). The writing too was interesting - it's not an easy task to write accessibly and provide real motives and red herrings. To my mind this one failed in certain respects - firstly there were too many motives and no logical pattern of elimination, and the red herrings were strait dead ends with no relation to the story, but what it failed at most IMO was clearly establishing enough differentiated characters - they were rather featureless, which made getting into them difficult. It's a tricky thing to do, and it has to be done with very few cues.
So here are a few characters they used - Law firm partner - serial philanderer
environmental activist - bunny hugger
Police investigator - rather obtuse

Now how would suggest they cue people in. What props would you recommmend (I am curious)