The Details are important _ Pay special attention to the details. They affect your readers very much. Details like alignment of the texts and the number of lines which your paragraphs include, can make readers bored or can interest them. Try not to make your paragraphs longer than 3 or 4 lines. When your paragraphs are short, people will read them easily. But if they are long, it will seem overwhelming to people. The colors you use in your newsletter design is important as well. So you should know a little about colors psychology. It's not hard. You must already know about the effect of every color on people, before designing or choosing your newsletter template.
A trick to writing fresh content on a consistent basis month in and month out is to learn to look at your topic from all angles and all levels. This is beneficial for your readers, because you are creating a library of information that covers your topic inside and out. This is also beneficial SEO_wise, because you are systematically creating a collection of resources that covers your subject backwards and forwards. This creates a greater chance of your article turning up for searches on every aspect of your niche. Last but not least__learning to cover your topic from all angles and all levels of depth is beneficial for YOU, because it forces you to establish your expertise in your field. If you are not already an expert in your field when you start writing articles, you surely will be after a year of consistently writing articles on every conceivable angle of your topic each month.