Regarding power cleans, you want the bar to graze your legs just above the knee. If you're doing it right it will grab at your shirt slightly as it passes by if you are wearing something slightly baggy. You will see a lot of people on YouTube that have it bounce off their thighs. You don't want that as it leads to a non vertical bar path. In other words, the bar will swing away from your body and then have to come back to you at the top of the lift. This is less efficient and gets you off balance since the back is pushing you backwards an down when you receive it on the shoulders.
In a perfect world the bar will go almost straight up and Down. If you take video you can upload it into this program called kinovea (sp?) that will trace the path that your bar takes. Pretty cool program and it's free. I will try to take one this weekend and upload with the trace feature activated.
Regarding chalk, I would highly recommend it. You can get a 2+ year supply from rogue for about $15 shipped.
Just hit 315x15 on my squat. Brutal. Almost puked when I was done.