For four boneless chicken breasts:
Marinate in one cup of lemon juice and one half cup of dry white wine.
Feel free to add herbs or spices to the marinade as you see fit.
I like a little salt and pepper, and maybe some of the Scarborough Fair seasonings. Sing it with me: parsley, sage, rosemary, and thyme. Though actually, I'll skip the parsley in this case, as the flavor's too "green", for lack of a better word, to work with the wine and lemon. The other three are pungent and a bit bitter. In an acidic dish they tend to come out as more aromatic and less bitter, which makes sense: bitter means basic, as in the opposite of acidic, which is sour.
A little marjoram and nutmeg might be nice, too. Not that I've tried that, but they're in McCormick Poultry Seasoning, so hey, it must be a good idea, right?
You can marinate for anywhere from a couple of hours, to overnight. Marinating longer will make it more tender, and more flavorful. I actually am planning to let the chicken soak overnight after I cook it tomorrow, which I haven't actually tried before, but I imagine ought to work as well, or perhaps better, though it does mean not being able to serve it hot without microwaving or otherwise reheating, which tends to dry the meat out. (I figure just putting room-temperature pieces into hot rice ought to work OK.)
Place a nonreactive pan (preferably stainless steel; with this much acid in play, anything else is going to get messed up, and you don't want nonstick because you want bits of stuff to end up getting burned to the bottom of the pan) large enough for all the chicken breasts over high heat, and give it a few minutes to heat up. Toss in the breasts, and sear til they've started browning on the outside.
Pour in the marinade liquid, stir around with a spatula to dissolve those bits on the bottom -- a silicone spatula like this is nice, as you don't have to worry about scratching the bottom of your pan -- then cover, and simmer on medium-low heat for twenty minutes.
Serve over rice, with a side of something that meshes well with sour flavors, like an artichoke, or some steamed asparagus, or a caesar salad. (Speaking of, I should dig up my recipe for caesar salad at some point.)