Absolutely don't talk about faith. That's a sure heckfire way enough to immediately turn an entire congregation against members.
Don't discuss differences in beliefs than the ones the preacher says. Thinking differently is not encouraged, and generally turns up trouble than it does any intellectual spiritual bantering. Keep your personal beliefs bottled up inside, and if you're of one of a thousand Baptist sub-beliefs, keep it to yourself. Or whatever.
Discussion of anything important, I think, is actually out of the question. I've noticed that when it comes to the big stuff, people just go "Umm...right" and then whip out their Crusader swords and begin slaughtering Jews and Muslims, and then each other.
It's odd. In my school, the most open kids to discussion of their faiths are ones who have no idea what they believe, and are swayed by anything that someone else says, "Yeah, I think so, too." And let it go at that.
Debate class...brr. Beliefs run high and deep, but just the same, no one cares to discuss them one lick. Because we have in our class alone atheists, Catholics, Methodists, Presbyterians, Jeohvah's Witness, Baptists, and unaffiliated Christians.
Makes for a boiling pot, except for the fact that the fire of a want to talk about anything particularly related to that God guy is not turned on. Which I think is good. Anytime we do discuss God it turns into the Inquisition, and I just want everyone to shut up, and I think everyone else feels that way. For the most part we all basically agree on the Jesus guy (the Methodist says God used evolution, and won't see a single argument against it, always going back in a circle to defend himself, interestingly enough, and the JW, I think, sincerely believes that the miniscule passage of the preservation of 144000 (Revelation) specifically means only 144000 out of all the millions who claim to be followers, will wind up on the golden roads. And the atheist doesn't believe a single word of it, clinging to some vague ambiguous utilitarian mask for most of the time).
I think as long as the central tendency of Christ is there, it's all good. If you're a kid among kids, don't open your mouth once. Even among adults, because most adults don't ever grow up from the kids they were, and when it's a spiritual matter, that's all the more true.
Then again, maybe not.