If you have an image you know you want to print B&W, should you de-saturate the image prior to the RAW conversion and then further adjust the levels in PS? Or, is it better to convert the RAW file in color and then take the color out in PS?

One of the best ways is to do the RAW conversion in color, then use the Channel Mixer in PS (with the checkbox labeled something like"gray scale" or "monochrome" checked) to get the best mix of channels. A simple "desaturate" doesn't give you any control over the mix of channels to use, but the Channel Mixer does. For example, you can choose the channel (R, G or with the least noise, or the most contrast, or whatever other good effect you're most looking for, and use more of that channel in the conversion to B&W. You might even just want to use one channel and ditch the other two.

Lisa

Or even do multiple conversions for different parts of the image. I've done this where the sky in an image wanted a different mix of channels than the rest of the image.

Giles

Lisa gave a very good suggestion, however, you might want to take a look at this method also:
Russell Brown Adobe's Russell Brown advocates use of a couple of adjustment layers (for which you could record an action to simplify matters) and it too works quite well.

Good Luck,
Ed