Re: Upstream or downstream....
Casting upstream and drifting down. Not only do you get a better drag free drift, but since fish face upstream, when they take your fly you are setting the hook towards the rear, right into the corner of the trouts mouth. The only downside side is the possibility of lining the fish. Long fine tippets and a well placed cast takes care of that.
Casting downstream, often times you will pull the hook right out of the fish's mouth when you set the hook.