The well brought-up are taught to avoid discussing religion and politics at dinner, while sex is never to be mentioned under any circumstances. But the following rules allow anyone to navigate the shoals of debate on these topics. The rules are infallible, incorruptible, and incontrovertible. Follow them at your own peril.
Political arguments are always heated and usually degenerate into an ad hominem attack. "You liberals have no spine," you might be told, or alternatively, "conservatives think more jails and more wars solve everything." Because you are intelligent and your interlocutor may well not be, you will be accused of being a Marxist. This is especially likely in the Obama era. You must reply, "of course I am. A Groucho Marxist. Whatever you're for, I'm against it."
On religious questions you might try to point out the illogic, indeed impossibility, of competing religions' claims to monopoly control of cosmic truth. This is unlikely to get you very far, since the true believer operates on faith not logic and makes a living from impossibilities. Better to confine yourself to the retort unanswerable:
"Have you found Jesus?"
"I didn't know he was missing."
The question of sex is far easier. If it comes up, and if you are male it often does, there is only one response. "Right here? Or shall we get a room?"