I suggest you play as much of this without a guide as you can without ruining the story.
That being said, this guide is absolutely incredible and highly recommended:http://lanoire.wikia.com/wiki/Cases
(Edit: The original guide disappeared. Wikia.com is usually a great go-to place for guides though, and this guide is as good as the original one that I posted.)
I found that I could miss one clue or one conversation topic and still get 5 stars. On one case I missed one of each and only got 4 stars, and had to replay that case. Also, let your partner drive *everywhere* (hold Y when you get to a car instead of just pressing Y to get into the car) so that you minimize property damage. I found that property damage caused during chases seemed to not penalize you quite so much.
As far as I know, dying or failing specific parts of a mission do not affect the 5-star rating. It appears that the 5-star rating is primarily based on your detective work rather than surviving, with penalties for property damage. Let your partner do all the driving and you can avoid mishaps in traffic. (I also found that I wasn't penalized, if at all, for accidents during high-speed chases. I have no idea what the threshold for losing a star for property damage is.)
You do not need to get 5 stars on your first run through. You can go back and replay the cases in which you got a lower score.