Choosing a newsletter topic is the first step needed to be taken by any newsletter publisher. It stands to reason that by knowing the topic you are going to write about will help in the creation of newsletter content, titles, and images.
When choosing the topic you should decide on something that you can produce interesting and regular content about. For this reason, as a newsletter publisher you should choose your topic based on one or more of the following 3 criteria:
1) Choose a topic which you are passionate about.
2) Choose a topic which you are interested in, and wouldn’t mind researching about when creating content.
3) Choose a topic with which you are knowledgeable (i.e. it could be related to your work).
Because many newsletter publishers are only producing newsletter to market a product, service, or website which they are already involved in, then the task of choosing a topic for those newsletters is already done.
For example if you are an affiliate or the owner of a site in the dog grooming niche, then that should be the core topic of your newsletter. You will find that in many niches there are opportunities to expand out i.e. in the dog grooming example you might be able to add in content regarding other dog topics and possibly other household pets.
You also need to consider the audience that your newsletter topic will attract. This will definitely have an impact on the style and content of your newsletter.
Another consideration that you will need to make when choosing your newsletter topic is how often you are going to publishing your newsletter. Many newsletters are published weekly, fortnightly or monthly, so you will need to choose a topic which will provide you with enough content.