1 Corinthians 3:6 - "I planted, Apollos watered, but God gave the increase." should answer the question of effectiveness. As long as we are prayerfully pursuing the sharing of the Gospel I don't believe we are damaging anybody... Recently, that verse is how the Holy Spirit encouraged me. There is this also, Ecclesiastes 11;1 - "Cast your bread upon the waters, For you will find it after many days." Finally, I guess we sometimes do your 1, or 2, or 3, and sometimes we do some combination of them. So, even though I am not a pastor, that is what I think you should keep in mind.