Unfortunately, I just recently paying better attention to my collection. I should have begun years and years ago.
Right now I'm just using paper. I have used Excel in the past but now any of that info is in two or three computers that crashed/died and are now stacked in my garage unusable. I actually did back up some stuff on floppy disks (yes, from the golden ages) but my new computers can't read them.
I am basically just keeping tabs on the prices I've paid for my coins. I've told my kids that when I pass I hope they can get at least half of my costs back.