In the early days of the Church believers encountered horrible persecution. Prison, executions, and more. And, yet, they survived. How? By "going along to get along"? By surrendering biblical principles in order to "reach the lost"? No. They survived and even flourished by remaining true followers of Christ. They were despised for their exclusivism -- "Christ is the only way; we can't honor your deities". They were hated for being different -- for being chaste and generous, for being exclusive of other religions but inclusive of all people, for prizing justice and making peace. They were out of step with their culture by being in step with Christ -- on the "wrong side of history" -- and, as it turned out, they drew in new believers and shaped a kinder, gentler world.
The positive impact of the early Church was not as much their message as their lives. People, seeing their difference, were then drawn to their words. Turns out that the same works today. The hot, "new" church growth method turns out to be teaching conservative doctrine and urging biblical living. Turns out that people who live biblical Christianity have a positive impact on their world as opposed to people who set aside biblical Christianity in order to have a positive impact on their world. That is, while innovation in the world may be good, innovation in Christianity is not.
What makes a positive impact on the world, then? "By this all men will know that you are My disciples, if you have love for one another." (John 13:35) There's one from the lips of Jesus. Here's another. "Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven." (Matt 5:16) In Acts 2:42-47 the early church in Jerusalem is described. It begins with "continually devoting themselves to the apostles' teaching and to fellowship" and includes a lot of sharing with each other and time together and "gladness and sincerity of heart". The passage concludes with them "having favor with all the people, and the Lord was adding to their number daily who were being saved."
What does it take to have a positive impact in the world? It isn't a rejection of God's instructions in order to get along better. It isn't better programs. It isn't hot, new trends. It is simple obedience. It is simply living out the instructions God gives in His Word in our living and our interactions. Not compromise; following and reflecting the Savior.