Okay, so the 'best' ending is likely 'New Life, Same Love'. To get that you must succeed in stopping Pierre. Since the game is branching and points based there are a few ways to do this, but the guide should help you with whatever branch you are on.
You can get the best ending on any of the routes. Framing him, corrupting his sister, helping the uncle. The guide should tell you how to 'win' all of them regarding the points needed and how the choices in the branch are scored.
