How do I know if I have high cholesterol?

A blood test. A simple, standard blood test is the way.
Get a lipid panel. Go to a health fair, your local public health office or you doctor and ask for a "fasting lipid panel." there are 3 separate goals: one for the hdl-c (good cholesterol), ldl-c (bad cholesterol), and for the triglycerides (bad little fats). Make sure you are meeting the goals for all 3. "high total cholesterol" is not important - we now know that each of the 3 parts are much better to use.