Most effective way? Who knows. While our conversations and example are great goads toward conversion, it is God who accomplishes a change of heart, not us.
I recently had a friend declare his intention to enter the Church. Months ago, when I knew there was a good possibility but he still seemed to have big issues to overcome I asked the FSSP (they offer a Mass intention slot with donations) to offer Mass for his conversion. While I can’t know for sure if this request was honored I can presume it was. And I know that although I had basically forgotten about that prayer request it immediately came back to my mind when I heard of his conversion. The point: it can’t hurt!
