Buidling a Relationship with Your List
I've talked in the past about the importance of building a list of prospective customers that you can send emails to when you have something worthwhile to offer. However, don't just focus on getting as many people to sign up for your newsletter as you can. The size of your list is important but worry more about building a relationship with your list so that they trust the offers that you do send out to them and you get a more responsive list. The old "size doesn't matter, it's how you use it" kind of thing.
Honesty
A person's inbox is a private place. If that person chooses to allow you into their personal space then you have to show them respect. The worst thing you can do is lie to them or severely over-exaggerate the offer you are bringing their attention to. Sure, a catchy subject line with an enticing body might increase your open and click through rates on that particular send, but if you fool them once they won't believe you in the future. The subscriber will opt-out and it will be a relationship that is burned for good.
Write to Your Ideal Customer
It's best to think about treating your subscribers like you do your friends. You want to write in a conversational tone, treat your subscribers like you would someone you care about, and connect with them. The best way to do this is to write each email as if you are talking to a single person. Your ideal customer. It's great if you actually have a friend or know someone who is interested in your niche because you can visualize sending the email to them. If you don't have anyone specific in ind then you have to get creative and really think about building a fictional character. Some questions to ask are what is the person's: age, gender, average income, fears, passions, the more details the better.
Relevant Value
It is also important to only offer your list products or services that will show value and are something they would be interested in. If they see you as a nice, good person who is truly trying to help them get to a place they want to be the response rates are going to be great for you. Not just in the short term with one particular send but in the long term as well.
Personal Revelations
You also have to remember that as you start sending to your list your subscribers will start to think of you as a mini-celebrity. You are coming across as an expert and are well-known in their niche (at least they think you are well-known since they know about you, everyone else should too right?). With that status you get this TMZ effect where they want to know more about your personal life and what you are doing. Revealing some information about yourself is important in creating a bond with your readers. Don't fill entire emails with what your eating schedule is like, but starting out with a "just came off the golf course and was talking with some friends about an idea I had" helps build the relationship.