I recommend that you should form the following two habits:
- Quote, offer and refer to your articles/eBooks/sites
- Quote, offer and refer to someone else's resources only for a certain compensation
Both rules should become habitual and be followed automatically; only then your articles and eBooks will bring maximum benefit to you!
If the reader enjoyed your article or eBook, he or she won't refuse to read one of your other subject-relevant articles or eBooks. Why don't you offer the reader to take a look at other works from your collection of ideas and knowledge? If you can't embed links in the article, you can create a section named "other related resources" in the end of the article and simply list the links there.
When you offer someone else's sites and products to your readers, you actually bring new visitors and potential customers to the owners of these sites and products. The main point is that if your article was helpful, the visitors have positive feelings towards this product! You have a right to demand compensation from the product's owner. If they don't have affiliate programs and don't offer commission for purchases made after following your link, you should negotiate another form of compensation (for example, links to your resources).
Finally. As an example, I'd like to take our product: eBook Maestro (www.ebookmaestro.com). If you're writing an article or an eBook about creating electronic books, explain how to compile eBooks using our program and provide a special link to it. All your readers who decide to create an eBook will buy our program, and you'll get 40% of its cost! Besides, you can get a special edition of the program where your affiliate links are embedded.
Alex Kaul is the owner of a lot of projects including www.ebookmaestro.com.