The problem with colour - B&W conversions is that different colours can end up as similar shades of grey resulting in an image with less contrast than you would like - also, traditionally, colour film is less contrasty than B&W, so conversion can look flatter than a "real" B&W picture.
The easiest way to get complete control over your conversions in PS
is to use Image -> Adjust ->channel mixer which allows you to manage the precentage each colour channel contributes to the final image. By adjusting these values, you can more closely replicate the look of traditional B&W film, as well as imitate the effects of colour filters on B&W film. Usually its best to make sure the total values selected add up to 100 (eg. red 60%, blue 20%, green 20%) but its fun to experiment.
Its also worth keeping in mind that with most DSLR's the blue channel usually contains the most noise, whilst the red channel has the least resolution (there are less red sensitive pixel sites on the sensor than for other colours - Foveon being an exception here).
Sometimes you might want to ADD some noise (filter -> noise) to get a gritty Tri-X effect.
As an example, here are some pub shots for which I did both colour & B&W versions - all shot using available light at 1600 ISO. Personally I think the B&W versions are more "atmospheric".
Colin K. Work, Pixstel