Ok, the point is that you use this unwritten rule: "The more you give the more you get"
When people know you, like you and trust you, they will be prepared to buy from you.
So how do you get this done, you might ask?
Remember these ration: sent 5 emails with useful valued information to 1 email with an offer!
To get newsletter niche material, check the Internet marketing forums and yahoo answers
YouTube and google itself