1 Corinthians 9:19-27 NLT

19 This means I am not bound to obey people just because they pay me, yet I have become a servant of everyone so that I can bring them to Christ. 20 When I am with the Jews, I become one of them so that I can bring them to Christ. When I am with those who follow the Jewish laws, I do the same, even though I am not subject to the law, so that I can bring them to Christ. 21When I am with the Gentiles who do not have the Jewish law, I fit in with them as much as I can. In this way, I gain their confidence and bring them to Christ. But I do not discard the law of God; I obey the law of Christ.
22When I am with those who are oppressed, I share their oppression so that I might bring them to Christ. Yes, I try to find common ground with everyone so that I may bring them to Christ. 23I do all this to spread the Good News, and in doing so I enjoy its blessings.
24Remember that in a race everyone runs, but only one paerson gets the prize. You also must run in such a way that you will win. 25All athletes practice strict self-control. They do it to win a prize that will fade away, but we do it for an eternal praize. 26So I run straight to the goal with purpose in every step. I am not like a boxer who misses his punches. 27I discipline my body like an athlete, training it to do what it should. Otherwise, I fear that after preaching to others I myself might be disqualified.

In verses 22-23 Paul gives several important principles for ministry.
1)Find common ground with those you contact.
2)Avoid a know-it-all attitude.
3)Make others feel accepted.
4)Be sensitive to their needs and concerns.
5)Look for opportunities to tell them about Christ.

Verse 27 to me is probaby the most important. When Paul says that he might be disqualified, he doesn't mean he could lose his salvation but rather that he could lose his priveledge of telling others about Christ. It is very easy to tell others how to live and then NOT take our own advice. We must be careful to practice what we preach.