Getting Your Knee Down - 101
A long corner where you spend a decent period at max lean. This is why roundabouts are good. On a short 90 deg corner, you are down and up again, without enough time to adjust attitude when at max lean. Obviously the corner should have a good surface, and, as you're prolly gonna have to have several attempts, not too much traffic or hostile neighbours.
You know how when you've been out on the bike on for a while, you start to feel 'in the groove'? This is how you should feel. Also, it means that your tyres will be good and warm
Approach the corner at normal speed, but brake earlier than normal - you want 100% concentration on peel-in, not on braking. While still upright, slide your bum over the seat, and stick knee out. You will need at least all of one buttock off the seat. Feet should be positioned with balls of feet on pegs. Knee should be stuck out as perpendicular to the bike as possible.
Now peel into the corner until you are leant right over. You will probably not hear the 'skreeesh' of slider straightaway. So, lean the bike over more. This may feel dangerous, but trust me, modern bikes are built to do this. Make sure you give it more gas as you lean, otherwise the bike will start to head for the inside curb. Also, being on the gas means you are very unlikely to lose the front. You probably feel like you are hanging off like a monkey, and leant over beyond comprehension. You are not. Like all new activities, it feels odd at first.
Didn't work? Ok, have another go, this time hanging off more. You can attempt to get more 'hang-off' while going round, but wiggling around on the bike while leant over can unsettle it, so prolly best left until you are more confident. If you just cannot manage it, there are several acceptable reasons : - you're body's the wrong shape (The Simon Batey excuse) - you haven't been riding long enough (The Rob Dymond excuse) - you feel silly/out of control ...this last is valid - on the road, you will definitely be going slower than if you just attacked the corner normally. On the track, most moderately quick riders get their knee down without trying.
Oh, and if anyone crashes trying this, then it is definitely *not* my fault :-) Have fun.