dissertation

[opiatelemur]

I apologize if this has been brought up before (didn't see it tagged though), but here's the thing: my future dissertation most likely won't have anything to do with my M.A. thesis and although I'm just beginning my doctorate studies, I'm just wondering as to what might be a good way to start organizing some ideas for the dissertation. I mean, I do have a general topic, but it stills needs so much more work before I could even mention it to my profs. Anyway, any tips as to organization? Also, has anyone here in the humanities decided to change their theme after writing an M.A.?

Thanks in advance.

upd I use a Mac.