If it comes up, and I share a little bit of my position, and they seem interested in talking more, I will talk more. But if they seem like they are decided, I let it alone.
I have a friend who was VERY interested in a birth book that I brought up to her, and we had a great talk about today's interventions in birth. She plans to have a baby in the future. Knowing that she seemed to be one to think critically about things and not just accept the norm as right, I decided to email her yesterday and also suggest that she look at the current CDC schedule, that some moms I know delay, skip, omit, etc and I had info if she wanted it. She said, you must be reading my mind, DH and I were just talking about this and I'd love to do some research. If she had written back and said no thanks, that would be the end of it - her choice.
So I don't push it at all. My SIL seemed open to discussions last summer and I gave her some info, never heard back. I won't bring it up again. She knows hwer I stand.
Generally, if there are people who know that I have a different position on vaccines, I will let them bring it up, not me.
Another friend is delaying and skipping many - only doing 4, and though I don't agree with those 4, I have chosen not to mention anything. She's done her homework on it.