How come nobody has yet mentioned learning to steer the bike with the handlebars, intstead of leaning? That would be the #1 skill to learn when dealing with side wind gusts. I learned this lesson the hard way when I was 20 years old, riding a Ninja 900RR at 220km/h and got hit by a side gust that almost put me in the ditch. I couldn't get the big bike leaned over fast or hard enough to counter it. Almost killed me.
I've since learned the skill. At speed, push the bars to the left gently, and the bike will lean right. Be careful, it can happen really fast. And it's weird to feel it. But it's the fastest way to flick the bike from one side to the other. Don't just crank the bars over, or you're going down. Just apply pressure, and you'll feel it happen. You have to practice this until you have it instinctual.
However, at lower speeds, the reverse is true. When riding single track in the woods, the fastest way to get around a tree is to throw the bike over with your weight, and steer into the corner.
There's a cross-over speed somewhere between the two techniques. Maybe 40mph. I think it happens when the gyroscopic effects of the wheels take over.