Keep categories few
Calendar, inbox, outgoing items and short-term reference are often enough.
Give paper an exit path
Processed items should move to action, recycling, reference or archive.
Align digital and physical calendars
Avoid maintaining conflicting systems.
Place it where decisions happen
A command centre hidden in an unused room will not become a habit.
Practical boundary. Measure first, respect product load limits, and do not improvise wall, ceiling or overhead installations when the structure or appropriate hardware is uncertain.