Our pilots details are all up on a whiteboard in the office. When a rating is due we get reminded and we book a flight test. We are supposed to be responsible ourselves as well but when you have a lot ratings (I have 13) that need revalidating on a constant cycle of tests it is easy to miss. Anything that helps has to be a good thing.
I am also a member of AOPA USA and they have a membership system that sends me reminders on my FAA CPL and medical etc.