Live seminars.
California requires that you take a six hour state approved live seminar before attempting the exam. In other states, it is generally not required to take a seminar, but you should anyway. Most notaries are shaky in their knowledge of notary concepts. You need to be on top of your skills, and a one day seminar is one way to keep solid on your knowledge. If you can't take a live seminar, sometimes there are e-seminars, or notary law primers for your state's notary laws.