Going in I had the first book planned out (this was largely due to the fact I had planned it out sometime ago but never got around to starting writing). I didn't plan it out scene to scene, but I knew all the plot points that would happen. Looking back now from the end of the first book (last post of it goes up tonight at 12:00, yay!)....I find I followed that plan pretty closely. Time frames have always been a problem for me in everything I write (always go to slow), and I realized about halfway through that nowhere near enough time had passed for several plot points. So...I started passing time faster, putting events farther apart, having characters make plans for next weekend instead of the immediate one , things like that. Ultimately I had to mix things up a little bit and tweak (just a little bit) where some of the characters are in their story arcs, but I actually think it ended up for the better.
As I got near the end of the book, I sat down at one point and did plan out everything scene by scene, but even then I didn't follow that entirely and when looking back over the notes while writing came upon some things that I just thought 'that's not needed...it's too repetitive and will slow the story down too much', and I skipped it.
And very occasionally I'll add new things in. So I'm very whishy-washy with my out line
For the future books of the series...I have a good solid plan what's going to happen in book 2 and then for after that it's more like I know the outline, the character arcs, the sketches of some events that are going to happen, but I don't have all the 'how's down just yet. There are large empty stretches I'm still clueless how I'll fill to get from point a to point b.
But part of what I love about writing without planning everything out is that I often will come up with ideas that way. If I sit down and try and plan everything, I'll come up with a complete blank. But while writing, I'll write a throwaway line or a small piece of backstory or a little action, and I realize it's the missing piece to a future plot line. And it all starts fitting in place, and then I feel like Hannibal Smith in the A-Teams, and think to myself 'I love it when a plan comes together'