1. Create new adjustment layer and choose hue/saturation.
2 Accept settings and set layer to colour.
3. Repeat the 2 steps abv but this time set saturation to -100.
4. Go back to previous "colour" adjustment layer and play with the setting to get the desired, tone, contrast etc.
I've this to offer, taken from The Digital Printing Handbook by Tim Daly.
1) Convert your RGB colour image to LAB mode.
2) Click on Channels palette and drag both A and the B channels into the Layers wastebasket.
3) Convert back to Grayscale before printing out or back to RGB for toning.