Everybody does metaphysics It is just matter of degree. Metaphysics is not just for high falutin philosophers with tweed jackets and pipes. The term probably throws people off quite a bit, and I sometimes wish there was a better one. In any event, the average person refers to being, substance, accidents, and so forth countless times each day. Human life functions around these concepts.
It is simply taken for granted that one is speaking truly when one says that their car is blue or that justice was served when the guilty criminal went to jail. And for something to be true means that it conforms to reality. Thus, at bottom, the correct notion most people operate under is that lots of different things exist, and it is just a matter of how they exist. I think this is a great bridge that can be used to have important discussions about subjects like God, morality, eternity, and so forth.
A common objection to God’s existence is that He is not discoverable by the five senses. If God existed, then scientists would have ‘found’ him by now, or He would be physically discoverable in principle. This objection gets dressed up in more sophisticated ways, but is ultimately predicated on an austere empiricism/scientism. And it can be shown that such an objection is inconsistent with reality as most (sane) people take it to be. To deny that we believe in things we cannot see, touch, hear, and test for is absurd. The skeptic will find it difficult to consistently deny mathematics, properties/accidents, and other non-empirically testable things, not to mention that science itself is underwritten by causality and other non-empirically '"verifiable" principles.
Thus, I suggest the common ground between the everyday skeptic and the theist is realism. And I think it is realism in the moderate, Aristotelian sense. The Aristotelian tradition encompasses the intuitions of the everyday person. The everyday person thinks that there really are such things as quantity, quality, time, and so forth. The Aristotelian paradigm says “yes, you are right…and here’s how that works.” Again, I think many theistic skeptics implicitly agree with the premises from which Aristotle formulated his thought. And it may also help to note that Aristotle carried no brief for the theistic traditions (Judaism, Christianity, Islam). We should pursue these means to have thoughtful dialogue, each side should discuss how we account for the things that exist.
Of course, there are theists that are not realists and do not agree with the Aristotelian framework. For the theists that are Platonist, I think the realist bridge is still there to a large degree. For the theists that are nominalist, I think they face a huge problem with internal consistency and will find it difficult to find common ground with skeptics. The discussion between the theistic nominalist and most skeptic will stall, because the theistic nominalist essentially asks the skeptic to discard his fundamental intuition about reality.