Once I know for sure I'm going to attend a meeting, I create a folder with a sensible name, listing the name of the meeting, the city and the year. This folder is inside another folder called "meetings, posters, talks, symposia". I keep these sorted by reverse date, so recently created folders are at the top if the list.
A copy of all correspondence gets saved to the meeting folder. This include emails about expenses, hotel confirmations, flight information, copies of presentations, etc.
This helped me out moments ago! I realized that I wasn't sure about hotel reservations for a meeting I'm attending next week. It took seconds to find the right folder, and pull up the hotel and meeting registration pdf. The pdf indicated that some of the hotel nights had been waitlisted, and that a final registration would emailed once that was resolved... but I never got that email.
I called the hotel, and confirmed that the reservation was valid, and that all the night were guaranteed, and now I'm good to go!
