Find and use your personal flags

Jason Sweeney has a very simple but effective way of remembering things to bring/do before leaving home next day, what he likes to call my blindingly obvious lifehack of the day: find and use your personal flags.

Now, why didn't I think of this? Lately I have forgotten my wrist watch in the mornings, the obvious solution is to place my glasses at the same place. Heureka!