[Brian]

My approach breaks down like this:

Hard appointments go on my calendar; I don't make every meeting I go to into an OmniFocus action.

Time-specific actions with a hard deadline go in OmniFocus with a due date/time attached. If I wanted to get something done before lunch, I'd probably enter "today, 12p" for example, so I get an alert on my phone if I haven't checked it off by then.

Items that I want to work on today and aren't naturally on my Due Soon list get added to the Flagged list. Once my must-do stuff on the DS list is taken care of, I work on the Flagged list and try to get as much done as I can.