It is worth at least pawing over maps before you go out - just going out and following road signs tends to take you along the shortest, busiest routes. I'm out to ride, not arrive, so seeking out the less direct way of getting places (or not quite get places then) is more interesting.
It used to be the case that I'd try and look out the most interesting circuit, but in fact some of the more interesting rides round here come from deliberately going along roads that are dead ends.
I tend to have stared at a map for a while before I go out, sometimes have a scan or print of the map in my pocket if I need my memory jogged, and sometimes have no real plan but a iPhone in my pocket to check my options. If you've planned a particularly detailed route then one of those little map holders on your bars is useful to save rummaging for a map too often, I find most on the market are too big/stiff, if found one thats about 5" square and soft backed, but I got it about 10 years ago from somewhere or other.
Had a great ride yesterday mostly on roads I've never noticed before, went out with half an idea, stopped to share jelly sweeties with a lovely veteran lady cyclist who gave me a mountain of tips and routes that lead to roads and landscape (and an especially fine eatery) on my doorstep that I knew nothing about.