Hello - and i'm new on this board -
Photoshop offers so many different ways to do this -
image > ajust > desaturate
image >
mode > grayscale
hsb > saturation slider..
but with all those above methods, you still need to ajust your histogram to get the wanted highlight shadows and midtones - curves does a good job at that. you can either play with the curve itself, give auto a try or manually set you black & white points on the image using the eye dropper.
but as mentioned above, my all time favorite is the channel mixer ajustement layer.. that way, you don't lose your original and you get more control over your zones. hope this helps a bit.