#5 -- Poor or Mediocre Marketing Materials
Cutting corners on your marketing materials can sink a ship faster than almost anything else. A professional photographer is worth hiring not because they have a cool camera, but because they have an eye to impress . . . they know lighting and angles . . . and because they have experience with what works and what doesn't! Anyone can take a picture with a digital camera, but the question is whether or not someone is going to present that medicore image to their client.
We all want to impress the people we could potentially work with. As an agent, I won't submit a talent whose marketing materials make our agency look anything less than stellar and professional. But thinking even farther into the process, what casting director would present a poor headshot to the director that pays their bills? In the talent world and the business world, ladders are climbed the same. If we impress those in a position to move our careers forward, we will likely get promoted [or book the job, in this case].
Talent who cut corners -- knowingly in the hopes that their skill set will compensate or just because they are naive -- commonly get pushed into the "we don't have time for you to waste our time" pile. Professional materials tell casting directors, agents, and directors that this is a serious endeavor; that you have something worth experiencing; and that you want to make quality films, television series, editorials, advertisements, etc.
If you were investing you bank account in another person's work, who would you choose to partner with?