Acting is acting. That is the general rule, but there are subtle differences that cannot be ignored. It’s therefore interesting that there are many different styles of acting, and different styles of auditions to go with them. But they’re all fairly subtle by the type of medium or the kind of project.
In each case, the kind of project you are auditioning for should be carefully investigated and you should prepare accordingly, in dress, in attitude, and in acting style.
Soap opera auditions are a little more formal in nature. The actor should be dressed up according to the character you’re reading for. Sit com auditions are more improvisational, and generally more physical in comedic acting style. If you watch an example of the show you’re trying out for, you’ll see that the camera shots are wider or looser to show more of the movement of the scene or the physical pratfalls or “gags” that are part of that medium. The soap opera shots are usually tight and theatrical.
An hour long drama audition may require a more dramatic approach to the scene you’ll read. More range in emotion may be required in a more serious scene. A feature film audition will be more relaxed, allow for ad libs if requested. Acting must be natural and casual unless the character dictates something different. As you see, it’s important to know your medium. Show you understand what style is appropriate for each kind of project.