You should consider what are the main types of readers that the journal has. You need to know about the reputations of journals in your fields, so that you can choose an appropriate journal to submit your paper to. It is a waste of your time and effort to submit your theoretical paper to a journal that only publishes practical papers. Many professional organizations have journals and newsletters. If you are a member, you are aware of them.
Some organizations allow only members to submit articles, etc.
It is a good idea to join professional organizations which are directly related to your interests. Once you have submitted your manuscript, it takes time for the editors of the journal to decide whether to publish your paper. If they reject it, you have lost much time. Even if they publish your paper, it may take one year or even longer from the time you submitted your manuscript until it comes out. Another disadvantage is that most journals have limited circulation.