There's a number of items that could be added to the list, but these are the ones that sprang immediately to mind. make no mistake, these can be hard lessons for an artist or band to learn, especially if they have to learn by their mistakes.
1. Treat Your Promo Materials Seriously.Anything that you send to a prospective agent, manager, booking agent, promoter or record label is important and can't be taken lightly. That means that you have to spend some time on it to make it not only presentable, but to show you in the best possible light. That means a professional picture, a good looking and informative website, and bios and promo with carefully created copy that's clean of typos and grammatical errors. If you're not good at any of this (most people are good at only one or two), that means you need some help. Ask your fans first to get the job done for free or inexpensively, but don't be afraid to employ a pro if what you have is not the best you can do.
Also make sure that any of the above industry people can easily get more information if they need it, so don't forget links to your website, music, photos, YouTube videos and social networks on any material that you send.
2. Understand What Makes You Unique.There must be something that makes you or your band unique. You've got to determine that before you pitch yourself to anyone. While figuring that out is up to you, here are two things to stay away from:
1) Don't say something like "We're different than anything you're ever heard!" Guess what, you're not. You may be different from anything that you've heard, but then you probably lead a sheltered life compared to people in the industry. Most industry folk have been around a lot longer than you and have heard a lot more. If aliens have taken you away to Area 51 to instill a new form of music in you, you better be prepared to back that up with some sounds. And if you think that your show is akin to Elvis and Hendrix rising up from the grave, you better have a YouTube video to prove it.
2) Don't say, we sound just like "xxxx (fill in the blank)" unless you're a cover band trying to get a club gig. You know what? There already is a Depeche Mode, Adele, Bruno Mars or Maroon 5. Record labels like to jump on the bandwagon of whatever's hot at the moment, but by the time they (and you) actually have a product to sell, the public has moved on and the whole thing dies. Be yourself and find out what's unique about you in order to get ahead.
3. Labels, Agents, Promoters, Etc Don't Care How Good Your Are.The music business only cares about one thing; do you have an audience. If you have one, that means you'll be able to sell music, tickets, merch and have a career. If you don't, it doesn't matter how tight you are as a band or how well you play. Just ask any jazz musician why he's not living in Beverly Hills for proof. Chops do not automatically equal audience (although it sure helps to have them).
In a future post, I'll add a few more of these. For now, take heed and be aware that these tips can save you a lot of time and heartache.