Remembering to do things

Why is it that so many people (a) fail to keep appointments--(b)forget to turn on the TV for a special program--(c) forget to take something along on a trip--and (d) fail to set the alarm clock ?
It is lack of a system to remember. I think there are two basic rules to make sure you remember:
(1) Take the necessary action IMMEDIATELY when you think of the something you need to do, and
(2) Fix a reminder you can't miss. For example: For (a) make a written note of the appointment in a date book that you frequejntly examine, or place a paper note at a prominent spot you frequently check. (Jan and I call this spot our Communications Center--a bare table in the front hall where we pass many times during the day).
For (b) ditto. For (c), the above or set the object in front of the door so you would have to step over it to get out.. For (d) same as for (a) and (b) with the additional possibility of setting the alarm clock immediately.