The FTC published a guide for disclosing relationships if you review/recommend/show products on social sites (and presumably your blog!). Link is to a pdf file.
- The disclosure should be placed with the endorsement message itself (as opposed to an About page, Disclosure page, or social profile page).
- If the endorsement is an image/video the disclosure should be superimposed on the image/video.
- Disclosure should be periodically repeated on livestreams.
- No lying (saying you used it when you didn't, saying you liked it when you didn't, making unsubstantiated health claims).