Before taking the written DMV learner's permit test, study the driver's manual to learn the rules of the road. You can get one from your DMV office, or you can download a PDF copy to read on your computer. Take practice tests online to learn about possible questions to expect.
Pay special attention to numerical values in the manual, such as the different speed limits, because these are likely to appear. Many questions have common-sense answers, but you can prepare if you pay attention to how other drivers handle certain situations on the road and retain that knowledge for the test, including the rules of right-of-way.