Him: I think we should go to France
Him: Then I'm wrong.
That's not going to happen.
I'm not now going to suggest that when you disagree you should say yes.
Him: I think we should go to Sweden
Him: Right, I'll get things organised.
Me: Shit... I don't want to go to Sweden
So perhaps there are two problems to solve. One: if we say no and cut someone dead, it ends the conversation somewhat and doesn't make them that willing to come up with another option. Two: if we can't say ABSOLUTELY YES, what can we say?
There's "yes... or"
Him: Let's buy a car
Me: Well, yes, or we could buy a van
Him: We could buy a van, perhaps an estate car would be big enough?
Me: Actually, an estate car would be slightly too small, but there are those vans which are also 4x4 trucks - how about that?
Keeping a bad idea open while you discuss alternatives is probably a bit nicer. Nobody has to back down if you're "or"ing.
For more on this see Six Thinking Hats which illustrates how to avoid going around in circles arguing the toss, rather than coming up with something useful.
But none of the above is the powerful bit. Let's consider a different scenario. Let's consider something where the outcome isn't "being right" or "accepting something". Let's just consider a situation where we're going with the flow. Let's also imagine that we're trying to be creative. In this situation gainsaying another person, trying to be the winner, is the opposite of what you need to do. You should, instead, engage the other person using the power of yes, and add to what they're saying. If you feel they're going off course, steer them aside slightly and see where you end up.
Him: Why don't we record an album?
Me: Yes, and let's try to do it all in one day?
Him: Yes, and let's try to do each song all in one take?
Me: Yes, and let's each play two instruments in those songs.
Him: Yes, and let's share the instruments, so the combinations change.
Me: Yes, and let's sing harmonies.
Him: Yes, and let's have an a capella bit in each song while we swap instruments.
Me: Yes, and let's video the recording sessions, so you can see how silly it looks
Him: And the album cover could be a montage of us juggling instruments and equipment while trying to be quiet
Me: And let's call the album "Silent Juggling".
And so on.
So here's the challenge. Next time you're out, talk a bit of bollocks to someone, a nice bit of banter. Make someone's day a bit more interesting, by being a bit silly. If they bite, keep it going. Whatever they add, agree to it, encourage them to play along more and more. It's fun. If you can't do it with a stranger, at the very least ensure to do it with people you know and love. It's way more fun to say "yes and" and then see what turns up.
Silent Juggling!? Really?