1. What do I do to prevent my action list grow too long (=longer than 50)?
A simple answer (perhaps overly simple) is contained in 4 ideas:
1. Write everything down (long list)
2. Process thoroughly to assess whether there is truly a commitment and how then to proceed
3. Weekly Review - if you didn't proceed, are you still committed?
4. Pareto Principle - 20% of your "work" yields 80% of the value. How much of the "bottom" 80% needs to be taking up space on the list?
Some people assign a notation for every time an item is deferred - 3 deferrals and it gets trashed. I don't worry too much about deleting old or procrastinated items - if they really are important they will resurface in a future mind-dump.