Rick chuckled softly as L'aire launched into her giggle fit. Apparently all the various implications of what he'd said had occurred to him before speaking.
"Well, first you need to make sure they aren't in a position to block it if they're armed. That kind of sweeping attack is fairly easy to pick off. So you either need to bait their weapon high or wait for them to get a bit careless with their guard."
"Then you want to make sure they're moving. Stances are key to any fight, and it's much easier to take someone off their feet if you can catch them in a moment when they're not rooted in one. Get them in a moment when they're not balanced perfectly and it's a lot harder for them to catch themselves in a fall. Maybe they only have one foot on the ground at a moment, a lot easier to sweep that than two. Maybe they're just landing from a leap and don't have their feet set well enough to be able to hop over your strike, etc. etc. Main thing is, it's an opportunistic attack. You can't launch it whenever you feel like it. And if it's something you want to use, and you see an opening, you don't hesitate. It might not last long."
"Of course, there is a way to pull it off even if they are all nice and balanced." He brought his staff around again, lightly tapping the back of each of L'aire's knees. "I've never seen someone good at keeping their feet after being hit there. Land a good blow," his smirk matched her own as he gently started applying firm pressure there with his staff to demonstrate the point, "and their legs will buckle, dropping them right to their knees."