I know it’s a bit stereotypical, but I learned to keep my schedule written out in front of me and always had a calendar / appointment book with my schedule and due dates handy.
When I was younger I was the dorky kid with a Casio electronic organizer and planner.
As an adult, these tools have evolved. Thanks to modern technology I am able to use Google Calendars and Outlook to stay organized. My mobile phone allows me to access these things easily from anywhere. Everyone has a phone these days so I hardly stand out because of this.
It is important that I use my calendar, and check it regularly otherwise I forget to do things and miss appointments. I need my calendar to be an efficient adult.