There are several ways to convert colored photos into black and white. Here are a few links and my attempts at each one. I'm curious to see which ones you think look the best.
This is the simple convert to grayscale that looks pretty mucky:
This one I converted to grayscale (deleting all the color information) then I converted back to RGB and messed with curves a little.
These next two photos are from a technique I learned from The Land of K.A. that uses a gradient map.
This one uses both lab color and RGB mode to convert to black and white: Design by Fire
This is a simple channel mixer method: For portraits set red:80, green:20 and blue:0 and for landscapes: red:70 green:20 blue:10. In any case your colors should add up to 100 percent. In this case I set red:45 green:45 and blue:10
In every case I applied an unsharp mask (20, 60, 0) and did some post dodging to bring out some hidden features.