I've not tried this, but...
Let's say you have a website related to health and there's a blog post on your site detailing how Fish Oil can help speed up fat metabolism.
Then, you join a 10,000 Group and post (as a FB profile) something like...
"Has anybody had any luck with Fish Oil, mixed with cardio? I've read here that it's meant to speed up the way your body metoblizes fat - what do we think, guys? {insert link here}.
So you post something that doesn't swear that a product works, it's merely asking for people's thoughts. I think it's important to come across as genuine and not to try and be pushing a product/service in somebody's face; but instead merely waving a carrot under people's noses to go and find out more.
Has anybody tried this method and how did it go?