Email marketing can be a very effect form of marketing and promoting products. The most important thing you should remember is that you are communicating with your list. If you are providing value through your emails then you are on the right path. There has to be balance. You cannot give value in one email and then throw a sales pitch in the following email.
You must remember that you are building a relationship for the long run. Use the triple-I method: Introduce, Inform, and Invite. When it is time to introduce a new product then it will be easier on you since you have cultivated the relationship and branded yourself as a leader, an expert, a teacher, and a reliable source of information. All you have to do is introduce the product without the sales pitch. Inform your list on how you use it and how it has helped you or just give an honest review. Last but not least is to simply invite them to test it out to see if they like it.
It does not have to be rocket science to be successful in email marketing. Just like in direct face to face sales, if you are in a bad mood one day you probably will not make that many sales. People will run from you. They also tend to run from you is you are chasing or being aggressive. Avoid these moods when you are putting together an email. Get in a good mood. Have some water and a snack. Talk to your friends, listen to music, or do whatever it takes to get in the zone or at least just get in the right mood. Don't send out an email when you are angry. That is a definite no go.
Be moderate with the CAPS LOCKS. It's just not proper etiquette to have a whole paragraph capitalized. Use it properly and only for words that you want to emphasize such as CONGRATULATIONS or HAPPY BIRTHDAY! Those are just some examples.