Two factors you should consider as well:

Feeling. Casting a show (and especially a season) isn't just about matching and pairing for dramatic compatibility: it's about picking coworkers as well -- so impressing the audition panel isn't just about performing well, but about selling yourself as a potential coworker. Loads of people who only did so-so at an audition wound up getting cast because the director liked the feeling in the room; loads of people who did out-of-the-park auditions didn't get cast because the director got a bad vibe and just could not see themselves working with this person. (And, yeah, it's a little childish and unprofessional, but it's a feature of every job interview ever conducted. Auditions are no exception.)

How do you nail the right feeling? Aim for professionalism:

• Emphasize adaptability. You're open to trying new things, you're "directable", you're the sort of person who doesn't mind jumping in puddles and getting a little wet.
• Dress well. Clean clothes with flattering cuts and colours. You want to look put-together and ready for work.
• Roll with whatever happens. If the panel is lighthearted and breezy, try to make them laugh; if they're stern and task-oriented, get down to business; aim for the centre of wherever the panel seems to be.
• Whenever you're not in character, be yourself. When it comes to this feeling-you-out-as-a-coworker stuff, it's very unlikely that you'll persuade the panel that you are someone else: far more likely they'll see right through you.

Preparation and Relevance of Materials. If you are not prepared to do the material we've asked you to prepare, you might as well walk right back out the door -- but even if you're adequately prepared, if the material doesn't relate to the role or the show, you may be sabotaging yourself.

The golden rule stands: never prepare materials from the show for which you're auditioning, unless you've been explicitly told to do so. In most cases it's advisable to avoid works by the same playwright or composer, too.

But if you're reading for the role of a 22-year-old contemporary graduate student ("two prepared contrasting monologues from other works + a cold-reading exercise"), and you come in with Prospero's soliloquy, even if you deliver it extremely well and demonstrate breadth as a performer, if someone else came in with a more relevant piece, and they read just as well, they've got the inside track on the part.

This is a delicate calculus: most people could not possibly prepare totally original monologues for every role they'll ever read for, and attempting to do so would involve sabotaging yourself as well. (The difference in quality between a monologue you've worked for months vs. a monologue you learned on Tuesday and never intend to use again...)

But if nothing else, don't just prepare a "stable" of two contrasting pieces then plan to keep them in circulation forever, especially if you're auditioning for the same company multiple times. If nothing else, consider that as you grow as a performer (and, frankly, as you age), you'll need to find new ways of presenting yourself in auditions, and you'll need new material which flatters or de-emphasizes different aspects of your performance. Approaching it with this attitude (ongoing process of finding new ways to flatter yourself) makes it likelier you'll have something relevant to plug into an audition when the need arises, rather than doing Prospero for the millionth time.