If you get stumped working on physics formulas, take a deep breath, and recheck your work. Go through these common physics-problem issues to make sure you have avoided them:
Mixing units
Expressing the answer in the wrong units
Swapping radians and degrees
Getting sines and cosines mixed up
Failing to treat vectors as vectors
Neglecting latent heat
Getting refraction angles wrong
Getting the signs wrong in Kirchhoff's loops
Adding resistors incorrectly
Getting ray diagrams wrong
