Reminders or notes? 😄
For reminders, I have a tool that emails me with an exact list of them on a specific day. E.g. You have to check this or that / create a report today. For a more important thing like a meeting or something similar - I set up a reminder on Google calendar.
I use my notebook on a daily basis to write down a list of things I'm going to do that day.
For docs and instructions for certain tasks that I repeat weekly or monthly, I have a whole document with a checklist on Basecamp - but that's a paid tool. For a free variant, I'd keep docs on Dropbox/Google drive and organize it in different folders.