Managers Tools - the key to Success!

Managers:

We've learned many tools to assist us in making decisons regarding our product, strategic position, market share and use of resources. Which one of the tools do you think is the most effective and WHY?

[Tools learned: SWOT, Planning Process, PLC, BCG Matrix, Porters Model]

Mission Statements

Does a mission statement matter? How does it help a business or does it?