1. Writing everything down
I make sure to write down every event, task etc as soon as I can, and then process it. This makes sure that I don't keep things in my head. Just this alone gives huge returns.
2. One week at a time
I organise my life one week at a time. First, write down all your time commitments for the week (things you've already committed to doing). Then look at the time you have left. Once you have that, look at your backlog of tasks/things you want to do (from element 1) and select the things that you can reasonably do in that week. I then schedule these tasks roughly for each day.
I found that setting a few tasks for a day meant that I was able to focus on one or two tasks, rather than dealing with the weight of all my different life facets at once. This was especially useful to me during university, when I was balancing multiple subjects and clubs.
3. Plan, record, reflect cycle
This part is quite simple, and could also work on its own. First you plan your week (See 2), then during the week you write down notes for yourself. This could be: - Where you failed (e.g. I was late for work today) - How you felt (e.g. I really enjoyed hanging out with x friend) - Any random thoughts/observations (e.g. I tend to get scared by strangers in hats)
I tend to set goals for each week, and then record relevant metrics (e.g. Hours on my phone if I'm trying to cut down, or days taking my medication)
Once the week is done, I do a reflection over the past week and look at what I want to change for the following week. Because I iterate weekly, there's no harm in me trying radical things with each week as an experiment.
Just the weekly iteration has been incredibly valuable for me, and has lead to some great insights.