I posted earlier about things I do to keep organised.
I'm delighted to have recently (re) discovered "The Bullet Journal" website. This is also a system to keep organised. It focuses around tasks and events: how to schedule them, reschedule them as needed, keep track of tasks in the distant future etc. Lots of people seem to find it very good. Check it out, www.bulletjournal.com. The homepage has a video and a text introduction that are good places to start.
One thing I see about it is that it doesn't explicitly include for is long-term goals, and deriving your short term and medium term tasks from the long-term goals.