Paul writing in Galatians brings verification of his preaching by retelling the story of his visit to the apostles. The big issue, of course, was the gospel coming to the Gentiles, but the one piece of common theological ground they had to have from Paul was this:
They asked only that we would remember the poor, which was certainly something I was willing to do. (Gal. 2:10)
While there was a lot of theological mystery and potential disagreement, one of the main things the apostles needed to hear from Paul was that he was still going to teach Gentiles to care for the poor.
Remember the margins. Remember the edges kicked to the curb and not having the resources to possibly “make it” in life.
The city where I pastor has a tremendous clergy group. We meet monthly and our churches together hold a Good Friday service annually. It’s a great group.
The real turn for us came several years ago. Every month we would meet and one particular pastor wanted to discuss our “distinctives.” He loved to talk about what was different in each of our denominations. It was okay to do, but after awhile it was irritating some pastors enough they didn’t bother coming as regularly as they used to.
We finally went through a process of asking, “What can we do together in the name of Jesus?”
When we had the discussions on what we could do together, interest picked back up. We have WIDE theological differences in our group. Yet, this is a group that truly loves each other because we want to see what Jesus is doing in the community and go to it.
Consequently, what “revs our engine” the most is putting things together that reach out to the margins of our city: the poor, the elderly, the at risk youth.
Remember the margins.
It’s probably because you find Jesus there quite often.
Apprentice 2 Jesus 
We just started working together to help with benevolence with 10 of our local churches. We pool money and volunteers to help those in financial need. The red cross is also involved. We asked the same question, “what do we agree on”.