Most of my rides are commuting and errands, or otherwise in fairly well known areas.

So, I hop on my bike, then start planning the route I'm going to take. Which paths, trails, and arterials through town. Which traffic lights to hit, etc. Usually I've planned a turn a few blocks before the turn... but occasionally the plan changes after I've already passed the turn and then I have to decide to backtrack or plan a new route.

If something is far out of my "normal", such as my recent Eugene to Portland ride, I did look at maps, and print out the Oregon Scenic Bikeway map and cue sheet before the ride, as well as choosing my bike and give my bike a general tune-up a couple days before the ride. I still was missing a few important details such as a total mileage as my planned route diverged from the Scenic Bikeway in a few places.

I suppose, if I'm generally familiar with the area, for a sub-century ride, I'll think of the start and destination and do most of the planning on the fly. It depends on other rides through unfamiliar territory. Perhaps plan parts of the unfamiliar routes (or print a map), and improvise the familiar parts.

Sometimes it is good to just hunt for new routes, bike paths, and experiences.