Spam is the biggest threat to organic search engines, whose goal is to provide quality search results for keywords or phrases entered by their users. Google's PageRank algorithm update ("BigDaddy") in February 2006—the final stage of Google's major update ("Jagger") that began in mid-summer 2005—specifically targeted spamdexing with great success. This update thus enabled Google to remove a large amount of mostly computer-generated duplicate content from its index.
Your first step is actually to go to your own site to get an idea of what types of people tend to visit your site and read your content. For example at Quick Sprout, we obviously have a lot of entrepreneurs, a lot of small business owners, a lot of bloggers, a lot of social media professionals that tend to visit Quick Sprout most often. It’s just a good idea to go to your site and just think of the type of people that visit it, because that’s going to guide you when choosing your Clickbank products. Once you’ve done that, your next step is to create a simple but effective spreadsheet just to keep track of all the products that you’ll be looking at.
Thank you for the heads up on seeking legal advice, I never thought of it that way. Has anyone ever experienced problems with closed door affiliate programs? I don't see how it would be ilegall in any way, but then if Chris says it, he must be onto something. It wouldn't be buying into an opportunity, because serious affiliates are getting it for free anyway. But I will still do as you suggest and seek legal advice.
If you have a good idea for an app, and the skills to create it, then producing your own premium app can be profitable. However, with so many free apps available, it may be hard to convince people to pay. If you want to go down the premium app route, consider having a basic free version to encourage people to download the app in the first place. You can then provide the option of upgrading to a premium plan once users realize how useful the app is.