I've been following the below steps for about an year now:

1. Go through my agenda for the next day every evening and commit to no more than 3 categories of tasks multiple, unplanned context switches don't work for me)

2. Try to religiously track my time. Easy to do for planned items but still struggling with tracking unproductive time. But within a couple of weeks, you start to see patterns even with such vague notes as (1230-1430: YouTube, etc)

3. Review your weekly / fortnightly patterns every Saturday. Takes no more than 30 mins a week to reflect on the well gone by and come up with one change to try the next week.

Orgmode has been a huge help with tracking the time and it ties in my workflow. And of course, the overall process itself keeps evolving, as it should.