When should I reset the SMC on a Mac?
SMC is short for System Management Controller.

The SMC manages hardware conditions related to temperatures and power consumption. Therefore a reset can only help in problems that are related to such.

Possible cases where an SMC Reset could be necessary include (according to Apple):


fans running fast but should not
keyboard backlight, battery indicator light, display backlight or magsafe LED behaves incorrectly
power button does not respond
closing/opening the lid does not work properly
battery not charging properly
system unusually slow