As far as body positioning is concerned:
Knee down on the road is really just for showing off.
On the track its used as a lean angle measure, you dont really need to do it unless your running on the edges of your tire and dont want to go off them, but it looks cool and its kind of confidence inspiring so most people do it anyway.
Anyway, heres the ideal way to take a corner in my opinion, im trying to remember css technique as much as i can, we'll assume your coming off a straight and going onto one:
1. Know your braking point, as soon as you reach your braking point, begin braking and start looking at your turning point, brake hard early and lighten up on the brakes as you get closer to your turning point (most people brake harder and harder as they get closer to the corner)
2. Set yourself up for the turn before you turn, toes on the pegs, inside toe pointed outwards, knee out, half your arse off the seat, just before you reach your turn point, switch your vision to your apex, as you hit your turn point, turn as quickly as possible and in one movement, i tend to move my upper body towards the inside mirror as i steer but i dont know if this is right haha.
3. As soon as your done steering (i dont mean when your out of the corner, i mean when you have the bike cranked over) start rolling on the gas to transfer weight to the back wheel and obviously to build up speed through the corner, you have to roll on suprisingly alot to even maintain speed as the act of steering slows you down.
4. Before you hit the apex change your vision to your product, the point you want to leave the corner at (basically) and start to straighten the bike back up for your straight. You dont have to use all of the track, dont run to the outside of the track just for the sake of it, run as tight as you can for your speed so you know how much faster you can go before your running off the edge.
Notes: Through all this your weight should be supported by your legs/outside leg and not on your hands, the bars are for inputs, not for supporting your weight or holding on.
Also, i make no claim that i can do all of the above, certainly not consistently, but you have to know where your going to get there.
Also, use common sense when applying the above, dont just roll on the gas if your going to die because of it, e.g your wide on thecorner and its off camber and youll be straight off the far side of the road/cars front if you gas it, just dont chop the throttle.