High Sierra and Dark Passage are both great. So is The Big Sleep. Anything with Bacall really.
To Have and Have Not is a good watch since it's when the first worked together. But I would probably wait a while after seeing Casablanca for the first time since it suffers by comparison.
Powder detergent is the way. When I open up the dishwasher at the end of the cycle and find clean dishes and no residual foam at the bottom of the machine I know that I used just the right dose.