Teachers should know that the quality of the answers depends significantly on the quality of the questions.
Knowledge is a unique kind of property, indeed: you can share it with others, while still possessing it.
Acquiring knowledge is the most fruitful effort.
It is equally important to learn from experience and from books.
Wherever you work, work hard and educate yourself continuously. You must never forget social welfare, ethics and honesty. However, there is no guarantee for your career progression. Therefore, don't expect that only the best people will be promoted.
Life is the greatest teacher because it educates even those who really hate to learn.