You might think that permit exams are not very difficult and you can pass one pretty easily without dedicating too much time studying for it, but you are not guaranteed to pass just thanks to some general knowledge on driving you might have. You do need to prepare if you want to pass on your first try, instead of wasting time and taking it multiple times. There are a lot of services available online that can help you with that.
The best way to get ready for a permit test is by taking a practice test. They are a pretty effective tool for everyone who is about to take a permit exam. You gain access to them online, and they are available 24 hours a day, 7 days a week, so you have no time restraints and you can take the tests when you want, where you want. These tests consist of questions that are based on the real DMV exam questions, so that you can get familiar with the subject and know what type of questions you will be facing when you take the actual exam. Example of a practice test can be found here: http://www.dmv.com/practice-tests
Another benefit of practice tests is that you have as many tries as you need, which means you can take them over and over again until you are sure that you have got the material mastered. Questions can cover various subjects, such as speed limits, safe driving, traffic regulations etc. On top of that, there are state specific questions, adjusted to rules and requirements that apply in various states. Some of those requirements can vary greatly from one state to another. For example, traffic signs or speed limits in Texas can be different from the ones in some other state and certain rules can apply only in that specific jurisdiction. More on Texas here: http://www.dmv.com/tx/texas
If you are planning to take a permit exam anytime soon, practice tests are the way to go if you want to make sure to pass the DMV exam with flying colors.