According to John Stott, Charles Simeon emphasized three things which he printed in capital letters in the preface to his works:
The Author...would wish his work to be brought to this test - Does it uniformly tend
TO HUMBLE THE SINNER?
TO EXALT THE SAVIOR?
TO PROMOTE HOLINESS?
If in any one instance it loses sight of any of these points, let it be condemned without mercy. (source)