Read Vol. 1 and Vol. 2 here and here.
1. Accept the fact that Your memory sucks
Get everything out of your head, even (and especially) if you are a genius. Write it down in a notebook, put it in your to-do-list app, on a note on your phone, on a post-it, or make a voice memo. It doesn’t matter how, but get it out.
2. Use As few tools as possible
There are new and amazing tools popping up every day, but make sure you pick a few that work for you – and not all of them (my go-to’s are Google Calendar, Google Keep and Any.do). It doesn’t matter what you use. Pen & paper are fine as long as you understand the next rule:
3. Routine beats tools
You need discipline, which means two things in order to stay sane, save yourself hours, prioritize, scrap useless tasks and (mostly) do what matters:
1. Plan your day either the night before or first thing in the morning.
2. Write a short daily log every night to become aware of what you actually spent your time on.