Andrew, I have to admit that I'm one of those highly organised loonies who documents, files and archives everything! I have a filing cabinet dedicated to all my web design projects, any documentation, emails or items/discs associated with each project is all in there! I find if I don't keep it organised I get really confused because there's only so much you can retain at one time especially if you have a couple of projects running concurrently!
My approach varies with the project but usually I start off meeting with the client on a face to face basis with a checklist of questions and take it from there really, I'm pretty down to earth so I prefer the meetings rather than emails/calls because alot of things can get lost in translation whereas I find having a sitdown chat is more productive, friendly and you can get a better sense of what your client is looking for too!
On the organisational side of things, I have an organizer and write out a to do list and just cross them off as I deal with each issue/item - I'm not one to follow an electronic checklist or filing system - I have to just tick them off otherwise I'm completely lost!
ps: I go through alot of post-its and highlighters too :lol: :shifty: