Last night Martin Salter spoke at our church in the series on Core values of our church. His was called Together and not separate. He pointed out that the very existence of the church (in both a universal and local sense), is a demonstration of this maxim. In bringing together so extraordinary diverse a group of people who belong to even the smallest church gathering, God's power is at work. So, rich and poor, sorted and unsorted, educated and uneducated, employed and unemployed and so on, being all part of the same body of believers is unique sociological fact. And meeting around the Lord's table (aka Communion) is a wonderful visual demonstration of this.
In Spurgeon's sermon Our Lord in the valley of humiliation, he speaks from the New Testament “And being found in fashion as a Man, He humbled Himself, and became obedient unto death, even the death of the Cross.” Phillipians 2:8, and considers how (strong-willed) individuals can be melded together in the church,
PAUL wishes to unite the saints in Philippi in the holy bands of love. To do this, he takes them to the Cross. Beloved, there is a cure for every spiritual disease in the Cross. There is food for every spiritual virtue in the Savior. We never go to Him too often. He is never a dry well or a vine from which every cluster has been taken. We do not think enough of Him. We are poor because we do not go to the gold country which lies round the Cross. We are often sad because we do not see the bright light that shines from the constellation of the Cross. The beams from that constellation would give us instantaneous joy and rest if we perceived them. If any lover of the souls of men would do for them the best possible service, he would constantly take them near to Christ. Paul is always doing so—and he is doing it here.
So what's the best tactic for fostering unity in a church? Take them frequently to the cross.