Here's what I do:
1. I figure out my ADRs. Any that I suspect will be difficult to get I push back towards the end of my trip, figuring that fewer people will have had access to those dates. Most of our ADRs tend to be for dinners.
2. When the crowd calendars come out, I try to reconcile my ADRs to the crowd levels. (But we always get park hoppers, so that's not a huge deal.)
3. We're rope drop people. I love being in the parks when they open, and I find we get so much done! I'm also our Fastpass runner. When we get to the park, we separate. My husband and the kids hang back, and I move close to the front. When the parks open, I get our first set of fastpasses, and meet them all at an agreed upon place.
For example, in the MK, I'll get us FPs for Peter Pan (silly, but we all love that ride!) and meet everyone else at Big Thunder. We'll do Big Thunder, Splash Mountain, then use those Peter Pan Fastpasses. (We're not huge roller coaster people, so some years we do Space Mountain, some years not.)
In Epcot, I'll get us FPs for Soarin', then we'll all do Soarin' together before heading over for Test Track.
In AK, we tend to stay together. We all head to the Safari, then head over to Kali River Rapids.
In DHS, we head over to Toy Story Mania, fastpass it and ride it.
Beyond that, we have a good idea of which rides tend to get very crowded, so we knock them off early in the day.
It's not a strict plan, but it allows us to see what we want without feeling like we've lost spontenaity.