Auditions are rarely the same. Casting directors are looking for all sorts of talents, acting styles, and "looks." Sometimes, the audition merely involves having a conversation with the actor. I have been to a few casting calls in which they simply wanted to see what an actor looked like in person. (Those were usually followed up with a brief nod and a "thanks for coming.")
Most calls involve some level of acting. During certain types of auditions (especially for live theater auditions), actors will be expected to have a prepared monologue (sometimes of their own choosing). For example, in the several productions of Shakespeare plays that I have participated in, I have always been instructed to select a classic monologue. Days before, I memorize the heck out of it, and when it's time to audition, I am given the entire stage to work my magic (or crash and burn).
As daunting as that might sound, most actors prefer arriving with a prepared monologue rather than dealing with the dreaded "cold reading" audition. Cold reading simply means reading the lines of the play (usually for the very first time) and doing one's best to display a character that the director will fall in love with.
Which one do you prefer? Cold reading or the prepared monologue? Or are they both intimidating? If so, check out my audition tips: