More active forms of reminders like alarms, calendar entries, date/time-based notifications (a common feature in to do list apps), or even just asking others to remind me help to keep me on top of things. It also helps to put things in a place where I will see them at the right time, if that makes sense. For example, my medication is in my bathroom because I'm there at the beginning and end of the day when I need to take my meds anyway.

At work, I have a kanban board containing a card for each task with due dates, a description, and any other info I need. The categories are various states the task can be in, including not started, in progress, waiting for someone to get back to me, on hold, etc. This works well for me because I have a single place with everything I need to keep track of and I refer to constantly, but this tool doesn't work at all for me in my personal life.

For things like emails and texts, I will mark items as unread after reading them if they have an outstanding action I have not completed yet (this also reminds me to make a card for it on the work kanban). Nothing leaves the inbox until it is completely finished. This works for both my personal and work tasks, in large part because I already check my email frequently. Sometimes I will email myself with a task in the subject line so I don't forget to do it.