When it comes to organising myself, I've long been anachronistic. I've relied upon paper notebooks for most of my life. In the last 15 years I've stuck to a particular type of diary/notebook hybrid, with a week-to-view on the left-hand side of pages and lined notebook pages on the right.
This worked well for me for my own personal stuff but obviously didn't work well for family things that need to be shared. Trying to find systems that work for both my wife and I has proven really challenging. The best we've come up with so far is a shared (IMAP) account and Apple's notes apps.
On iOS, Apple's low-frills note-taking app lets you synchronise your notes with a mail account (over IMAP). It stores them individually in HTML format, one email per note page, in a mailbox called "Notes". You can set up note syncing to the same account from multiple devices, and so we have a "family" mailbox set up on both my phone and my wife's. I can also get at the notes using any other mail client if I need to.
This works surprisingly well, but not perfectly. In particular synchronising changes to notes can go wrong if we both have the same note page open at the same time. The failure mode is not the worst: it duplicates the note into two; but it's still a problem.
Can anyone recommend a simple, more robust system for sharing notes — and task lists — between people? For task lists, it would be lovely (but not essential) if we could tick things off. At the moment we manage that just as free-form text.