I find that most Parisians (at least those to whom I've had the opportunity to faire la bise) start by leaning to the left so the right cheeks touch first. And two kisses, definitely two. About air-kissing, I would like to add this: it will look ridiculous and chichi and hypocritical if you overdo it and don't even touch cheeks with the other person, but you are not supposed to kiss the person's cheek full on, either, unless it is a very good friend and you want to express your affection. To me, la bise is more a brushing of the cheeks than an exchange of actual kisses. (And this is especially important if you're wearing a fresh coating of lipstick.) I've also noticed in recent years that it has become more and more common to reach up and place a hand on the other person's upper arm (same side, just below the shoulder), as you kiss him/her, even if it's someone you're just getting introduced to. And I second Ptipois's note on men bise-ing each other, although I've only seen it done in a context of friendship, and never on a first encounter. Clotilde.