This is tricky advice to give. Feel free to disregard, of course, as this comes down to style. And that is a personal choice, and there are many forms of it.
But one frequent and serious complaint I hear from those working and hiring is that people reach out with far too much casualness and informality when trying to connect with them. You might think I hear this from the older crowd, but I also get this from 25 year olds. When you are trying to connect with someone, they are not your buddy or your friend, nor likely do they want to be.
People in the working world often feel like they are doing you an enormous favor by merely taking a moment in reply to your query. I don't think this is entirely right, but most do feel that way. Nearly everyone in the field struggled when they started. They tried to reach 100 people and prayed one would respond. They know how hard it is. The business can be humiliating and those working now suffer are often still slammed on a daily basis. So when they do take a moment to interact in a moment of human kindness with a student and the student appears arrogant, casual, jokey, flippant, or demanding, this just does not go over well. You may think it's wrong they think they are doing an enormous favor by interacting with you and it's no big deal, but it is a very, very big deal and your behavior should reflect that. You may say, "But hey! My friends think I'm amazing!" Or "I'm going to smack this guy at DreamWorks like I do my friends to show how cool I am!" I can't begin to tell you how little that means to people in a working office and how annoying they usually find it.
People who are polite, considerate, express deference, and offer profuse thanks do far better in reaching out, establishing, and maintaining a connection. You may also say, "I heard this story about this guy who told this show runner what his show sucked and got hired!" or "I told her to her face I thought her film was bad and she respected me for it and hired me!" Those are called “stories.” Stories do happen, but they don't happen much. That's why they are stories. If Odysseus had a leisurely three-week cruise home through the Aegean Sea after the Trojan War, we wouldn't still be talking about it. Feel free to dismiss this. Seriously. But if you are reading this and saying they guy doesn't know what he's talking about and that's not how I roll or who I am, there's a good chance this is actually about you and you don't get it and you're doomed before you even begin. If you are an artist, also feel free to completely disregard. Charlie Sheen consistently works.