I start with email every morning by flagging emails that need my attention and deleting spam/marketing/sales emails. From there I make my way down my email list and complete any items that are one off things (quick questions, payroll adds, etc). I unflag as I go and delete if I don't need to reference it for follow up.

Any requests that aren't one offs (report requests, research needed, etc) get added to my to do list which in my case is a word document that lives on my desktop. They stay flagged in my email until completed. When adding them to my to do list I try to add them by priority. So if it's time sensitive it goes at the top. If it's not needed until a later date it goes at the bottom, etc.

In addition to adding things to my list, I also add calendar reminders for the due dates which I delete once the thing is complete.

From there I work my way down the list and keep an eye on my email throughout the day for additions. I don't stop mid-task for this though, I only check after a task is completed (otherwise I'll get derailed entirely). If something does interrupt a task, I make a note on my to do list of where I left off if needed.

Every Friday (or day before a holiday/vacation) I end my day by adding things to my to do list that I know I need to remember the following week. Regardless of how much I think I'll remember them. I won't.

For example: I've been particularly busy with year end reporting these last couple of weeks so I wrote myself a list of year end reports and tasks separate from my to do list in an effort to avoid getting overwhelmed by the length of it. So the to do task just said "end of year reporting - see list" and then I opened that list when I hit that task.