There is at least one program which generates a schedule for you to follow, if you like that sort of thing. There was a little bit of discussion of it here a few years back, but I don't recall the name. Ah, I found it:
http://skoach.com/
I work the items most immediately due, then draw from items starting today and flagged items (set up during my reviews). On the very productive days where those lists are completely exhausted (or I can't get any more done without being in a different context), I open up the context lists and look for high-value tasks in my current context(s). I use flags as a way to draw my attention to actions and projects which may or may not have immediate time pressure but are nonetheless items on which I wish to focus my attention. If I determine during my reviews that a project isn't making adequate progress, I will flag the project or perhaps the first few actions.