Romans 12:16 - "Live in harmony with one another. Do not be proud, but be willing to associate with people of low position. Do not be conceited." (NIV)
I find that, even in church, there are still divisions and cliques among us. If there is one off-putting thing about churches to people is that often we fall into a worldly pattern of becoming exclusive and we don't branch out to include others into our groups. However, the Bible reminds us that we should not exclude people. We need to love one another and reach out to others. Too often we are self-absorbed, and the Bible clearly asks us to be hospitable and get outside ourselves a little bit.
It's not easy. When we go to church or school, we like to see our friends. We like to hang out with people we know, and getting to know others is sometimes uncomfortable. Yet, think about it...how would you feel if you were the kid eating by himself at lunch every day? Or the person who walked into youth group for the first time? As Christians we need to exemplify that God loves everyone by, well, showing that love to everyone.