Maybe you've heard the rule already -- touch it once.
I'm not sure where it came from originally, but it's a fantastic rule for productivity. Once you open up an email, a piece of mail, or something else that needs action, you don't do anything else until the required action is dispatched. A lot of time, mental energy, and stress are wasted by looking at something repeatedly.
So, you "touch it once" -- after looking at it, you immediately take action on it. If you can't for some reason, say because you need other information, you at least explicitly define what information you need.
It's really a fantastic habit to get into, but one of the hardest parts of it is subtle -- to only touch things once, you need to refrain from going through them when you don't have time to dispatch them.
This is hard, but worthwhile. Once you start refusing to open your email until you're ready to clear it, stress goes way down and productivity goes up.
It's hard, though. Not easy at all. But very worthwhile. Touch things once. And don't touch things you can't take action on right now.