I like all being said, but I'd like to caution against one thing that has been suggested very often: discussing things OOCly. Of course, it takes away a good deal of problems, but arranging everything in advance also takes away the fun, the mystery, etc.
For example, if I know someone won't accept a kiss, then probably my toon won't attempt it. And yet, if I didn't know the outcome in advance, he might have had.
So I'm more in favour of the consequences idea someone mentioned. If you don't godmod, and portray well the strengths and weaknesses of your character, then you shouldn't need to ask except for key/important things. Else, just act and see what happens.
In the essence, I believe fairness boils down to one thing: respecting the other.
Content generation! And really, who in a few years down the road would even remember such an incident, anyways? I can remember some really out-there stuff that happened at La Maison, that thankfully few of us remember. Time heals these types of wounds... as opposed to knife wounds, or scars, or things of that nature. Those are the serious kinds of godmoding maneuvers that should be watched out for, dilligently.
Oh, but some of us still remember.