I use double opt in if there's only a one-way benefit but this happens rarely, maybe 10% of the intros. Usually, when I'm introing, I try to find mutual benefit

I use double opt in if there's only a one-way benefit but this happens rarely, maybe 10% of the intros. Usually, when I'm introing, I try to find mutual benefit and state it clearly in the email. I find these intros both easier to write (since it's not an expenditure of social capital on my part) and, generally, way more appreciated by both parties.