Nothing is a bigger waste of time than not taking a few minutes to know something about the person you are contacting before you reach out. You'll just wind up writing something completely irrelevant to someone who can't even help you. It's useless. Find your inner Sherlock and take some time to do a bit of detective work online.
For example asking me to write about your music, or to promote your event that isn't open to students, or to listen to your demo just shows you didn't take even the most cursory glance at this site before you contacted me. Take the time to understand what that person does and think about whether or not they could actually help you (this doesn't mean they will or can but at least you'll improve your chances). You wouldn't walk up to a random person in a store and ask them to help you find something would you? You'd probably seek out an employee who knows what they're doing. Don't contact an agent asking for a record deal or a publisher asking for help getting a show. Don't just send out your demo to anyone you find who works in music. Frankly, it makes you look ignorant and unprofessional and it's downright disrespectful to ask for help without even paying the slightest bit of attention to that person. At best, it will annoy the person you contact and guarantee you don't get a response. At worst, it could turn you into an industry black sheep if you do it to enough people. Don't take that risk. If you're already putting the effort into finding people to contact, it doesn't take much more to actually find out something about them and consider what you want to ask. If you expect people to be respectful of your work and your time you need to treat them with that same respect and realize that there is a fine line between asking for help and spamming.