We have a lot of our "bigger" talks in the car, while one of us is driving. Since we're trapped together and can't escape, might as well
If that doesn't pan out (like if it's something we don't want to discuss in front of the kids, at least one of whom is always in the back seat) we frequently find ourselves chatting in the kitchen while preparing a meal. We made a huge life decision (a move) in the kitchen just a few weeks ago, in face. It's also a time when we're kind of "stuck" in one place together, so I guess that works for us.
Also, after a glass of wine on the couch, in between DVR'd TV shows.
I don't plan sit-down talks though, because then I feel like it puts The Weight of Expectation on things.