Ask HN: How do you recommend things to your friends?

If you want to recommend something, where do you go? Twitter? Facebook? Topic-specific networks like Yelp, Goodreads, thesixtyone, etc? Email/IM?

Similarly, if you're looking for a recommendation, do you use Vark? Google? Twitter?

Since I know someone's going to say it: Yes, I'm using HN for research. Is there something wrong with that?