Can you spot influencers? Do some Google searches for terms or keywords related to your topic. Do many blogs or informational content appear in the search results? Do these blogs seem to have authority? Are the readers engaged and commenting on posts or does there seem to be a strong social following? Strong engagement or following tells you there is an audience for the topic. Note the blogs and social influencers within your topic, and jot down what you like about them or feel is missing from their content. This research will come in handy later as you plan your content.
Be sure to check what kind of customer support you can expect from your affiliate program once you have signed up. Do your research online and if possible, speak to other sellers using the program to get their thoughts. Can you speak to someone via phone or Skype or do you have to wait 72 hours for email responses? Be clear on this because trust me, you will need support at one point or another.