Here's a lovely #bulletjournal set up that doesn't look too overwhelming to do: https://www.youtube.com/watch?v=_uLC_V98CSc
I love Yukiko Sakamura's planner advice! Here she talks about #planner slumps, and what you can do when they happen: https://www.youtube.com/watch?v=T9gP3MlbCQw&t=19s
JetPens posted an overview of the Roterfaden Taschenbegleiter Organizer System (honestly, it's a fancier Traveler's Notebook). Luckily, I cannot afford one: https://www.youtube.com/watch?v=4RnUDFgzx4E
Lastly, MissTrenchcoat on planner mistakes: https://www.youtube.com/watch?v=pHoQuw10HKo