I'm also a bit half-and-half on this. The vast majority of my work at the moment is based on pinhole self-portraits, and all done in the same place. That's fairly carefully planned, with an idea of what I want to try or explore in that session, with whatever set up I need, and then I go with what happens based on each exposure. With the portraits, mostly the same, but it develops based on the subject: who they are and what they are bringing along in terms of mood, intention, and reaction.
The travel work is entirely different: i don't know what I'm going to see until I get there. The oddest, and most rewarding part of the pinhole-in-morocco expedition was a day spent doing street portraits where I gave myself strict rules (only one exposure of each person, no meter, just a chat and then a picture). But on the whole trip, even when I scouted around before setting up, I found that the "first thought" picture was usually the strongest of the set I made in any given place. Over-thinking killed a lot of shots.
And then I do a lot of drive-by shooting too, hanging out of the car window, and taking pictures of fields and trees and skies. But even that is a bit more planned than it seems: I know the route so well, and know pretty much every tree along it, so I'm trying to get particular shapes in particular places, and double them up with the next known landmark I've got tagged in my head. I think too much.
