How to Solve It by PĆ³lya

Understand the problem, devise a plan, carry out the plan, and look back.

Understand the problem.
 What is the unknown?
 What are the data?
 What are the conditions?

Devise a plan.
 Have you seen the problem before?
 Do you know a related problem?
 Look at the unknown!
 Here is a problem related to yours and solved before: could you use it?

Carry out the plan.
 Carry out the plan and check each step.

Look back.
 Can you check the result?
 Can you check the argument?
 Can you solve the problem differently?
 Can you see it at a glance?
 Can you use the solution or method of solution to solve some other problem?