I shifted from text-files for todo lists to using an adapted Bullet Journal 3 or 4 years back. Some times I neglect it for a few weeks at a time, but I've found it really useful on the times when I have used it extensively. In many ways, the todo section has similarities to Kanban.

But anyway, one convention I picked up from there is:

      - for a comment - something to remind yourself of the context or information to remember
      . for a task you want to do
 date . for a task that needs to be done on/by a certain date
      / for a task that is started
      X for a completed task
      > for a task that moved to a later page

It's a great system especially as transition from one state to another is just the addition of a line so very easy to do with pen and paper. Also, the act of transferring uncompleted tasks to a new page every week/month depending on preference makes it a great time to assess if things on the todo list are still worth doing as well as giving you a gentle reminder to get on and do them if they are.