In my entire portfolio I have 2 black and white images so I'm obviously not an authority on black and white conversion.
That being said, let's take a look at the B&W Panel in Adobe Lightroom 3. Using this panel to create black and white versions of your photographs is only one option within Lightroom. Simply select the image you'd like to convert and click on the B&W Panel. Shazam! Instant black and white. Like the HSL Panel, you can use the Targeted Adjustment Tool (TAT) to adjust the original color areas to provide greater contrast within the image while fine-tuning the "shades of grey" for greater effect.
The above is the exact approach I used to adjust this image, titled "Harbingers". I also used the Tone Curve Panel for even more contrast and then added some additional grain to the image for that "late night horror show" look.
Obviously there's a lot more to getting attractive black and white prints than what I've contributed here. Again, I'm not an authority. If you haven't purchased Scott Kelby's "The Adobe Photoshop Lightroom 3 Book for Digital Photographers" yet, you may be happy to know that he devotes an entire chapter to converting images from color to black and white. I skimmed through it again before preparing this blog post and it really does contain some really great information. From helping to identify which images would look good as black and white to the various means of producing and editing them in Lightroom, you'll find it is certainly a worthwhile resource to have in your own library.