I mention a lot of products in my posts. This is because I want to share the products I like that have been working for me. No one is paying me to endorse their product.
I have, however, signed up with Amazon Associates and Google Adsense.
Amazon Associates: I will receive a percentage of any books bought using my links. No one tells me which books to recommend. I will only recommend books that I have personally read, like, and refer to on a regular basis.
Google Adsense: I have allowed Google to post ads on my blog. (They are supposed to relate to the content.) This has absolutely no affect on what I choose to write.