I go into many of my shots with a vision of what I want, but since 75% of my shots are waterfowl action shots, it really gets into luck of the draw. I know exactly what I want and set myself up accordingly to capture that, but controlling what the birds do is a trick I have yet to master!
However, I think every planned session should have an outcome in mind. I know what I want to achieve, I scout the area and determine the best options for achieving that shot, then plan on luck and (I like to think) a bit of skill to pull out what I want. In doing this, I usually take a lot of shots during the session and then pick the best out of what I get. In a normal day of 3-4 hours of shooting, I feel lucky to have 4-5 keepers for the day.
Then there's the rest of the time. I love driving the mountains and hiking the trails and there's really no way to plan for a moose walking out in the road, a deer jumping a log, the perfect conditions at a small mountain lake perfectly reflecting the early season snow in the mountain peaks as the trees surrounding the lake glow in late fall glory... Yeah, those can never be planned but those, combined with the experience, are what really make the hobby worth doing.