Find out what topics you'll be tested on and if you are allowed to bring any props, visual aids, and how you should dress.
Be sure to prepare for the oral exam as you would any other exam.
Anticipate questions that may be on the exam. Prepare answers for the questions and then ask/answer questions that you think might be asked with another person, preferably with someone in your class who knows the material.
Practice talking in front of a mirror so that you can evaluate your body language and/or record your answers on audio tape and play it back to see how you sound or on a video tape to see how you sound and your composure.
If you are using a computer or other equipment for your exam, test it out several times and make sure everything is the way you want it to be.
Show up at least a few minutes early so that you can gather your thoughts and not feel rushed. Being late may also have an adverse affect on your grade.
Turn off your cell phone before taking the exam.
Maintain good eye contact and posture. Don't slouch if you're sitting or lean if you're standing.
Pay close attention to the questions asked. If you don't understand the question ask for clarification or ask your instructor to repeat the question.
Speak in complete sentences. Try not to give one or two word answers, whenever possible.
Be sure to thank the instructor for his/her time when you are finished with the test.