Keynesian Economics and Fiscal Policy

When the economic theories of the Classical Economist were not sufficient to put an end to the Great Depression of the 1930s, government leaders began to look for other ideas to help end the problem. The British economist John Maynard Keynes argued that the economy could not always self-correct.

1. What can be done to increase consumption in a depressed economy?
2. What can be done to avoid depression in the first place?
3. Would it be correct to say that the ideas of the Classical Economists are fine when the economy is prosperous and that Keynesian Economics is better when the economy begins to deteriorate?