I do a lot of black & white photography and a few friends have asked me how I convert my color digital images to black & white.
I ended up doing a video of how I do it in Aperture and wrote a quick summary in my website.
Basically, I first convert to black and white using the Monochrome Mixer and playing with the Red, Green, and Blue sliders to get me close to where I want to go. Then, and this is where the real power of Aperture comes in, I play with the Luminance slider in each of the colors in the Color brick to lighten or darken individual areas of your image based on the original colors.
It works for me... but not all of my photographer friends are using Aperture. Does anyone using Lightroom know if it's possible to get the same level of control? I'm guessing yes, as they're both great programs.