I keep a written log of my meetings and to-do lists on a science type notebook in blue ink.
When I am doing research, work, or investigations, I keep a synopsis of what I read in a word document and do all my calcs in excel. These are then searchable.
Key emails I also transfer to word and file away.
Everything is filed under a year -> customer-or-subject ->-subject-date system.
I keep a separate word document where I put down ideas. If I have time, I will elaborate a short white paper or biz case excel.
This has worked out very well.
One my best direct reports also prints everything out and keeps it in binders based upon tasks. This allows her to work no matter the situation.
The smartest person I know records everything in synopsis form on his laptop - meetings, work, you name it, and then files it away. He has 20 years of his work cataloged and can refer to just about anything in minutes.
Being organized not only leverages effectiveness, but takes the wind out of confrontational coworkers, clients, and the odd lawyer.