Maybe more obvious to some more so than others, using a single monthly log can really help get organized.
I never used to do this but when a entered everything on an excel spreadsheet with column headers, in order of due dates - payments are never missed or overlooked.
Followed at the based by row reminders throughout the year. For example, when to call Direct TV by, in order to extend our yearly plan (so that rates don't rise).
You might also put warranty expiration dates so that items can be inspected for possibly making claims just before the option disappears.
The 'single page system' can make it easy.