The teacher can seldom afford to miss the questions: What is the unknown? What are the data? What is the condition? The student should consider the principal parts of the problem attentively, repeatedly, and from from various sides.

The open secret of real success is to throw your whole personality into your problem.

If there is a problem you can't solve, then there is an easier problem you can't solve: find it.

If you cannot solve the proposed problem try to solve first some related problem.

I am too good for philosophy and not good enough for physics. Mathematics is in between.

Geometry is the science of correct reasoning on incorrect figures.

In order to solve this differential equation you look at it until a solution occurs to you.