People are good at adapting their environment in order to remember things. This is specially true for things they have to do in the future (prospective memory) and thing they have done in the past (autobiographical memory), but applies to other kinds of knowledge too. Examples are writing various kinds of notes (e.g., a list of things to do) and placing objects so that they are in view (e.g. placing letters to be posted near the door so that they're not forgotten). Some techniques are specific to certain jobs (such as aircraft pilots removing a glove as a reminder that a task is unfinished) or to certain cultures (such as tying a knot in a handkerchief as a reminder that something needs to be done).

How do you adapt your environment to help you remember things? How might the kinds of "external memories" you create provide inspiration for designing memory aids in user interfaces?