Dress the part. Dress for the environment you'll be in when you're auditioning. You should also consider what type of position the audition is for when choosing your wardrobe. Dress like others in your position would dress for a similar audition.
Have someone shoot the video for you, if possible. It is best if you use a tripod and have steady camera motions. But if you're planning movement in your video, having a friend or family member run the camera is preferred. Having someone shoot the video for you ensures that you will be properly framed and that colors will look good for you and will ultimately save you time in your audition video.
Speak professionally yet naturally. You want to come across on your audition exactly how you would be speaking when you'd be in front of the camera while shooting for the gig you are seeking.
Prepare what you are going to do and say on camera. If you are not used to performing in front of the camera, practice what you will be doing and saying until you have it down from memory. Remember not to sound rehearsed. You want to come across as naturally speaking to the audience.
Light the shoot properly. Shoot the audition with light coming toward your face not toward your back. Lights coming from behind you during the shoot will cause you and what you're doing to appear washed out on camera. Lighting the front of you will look professional.