One tip I found usefull was to shoot raw+ large jpeg, set your camera to shoot B+W (not sure where it is in a nikon) this way you have the best of both worlds.
You have full colour raw, which will give a better B+W conversion in photoshop or whatever, and you have the added advantage of "seeing" the images in B+W on the back of the camera (from the jpegs) so you can see whats working and whats not working.
As a long time B+W film shooter it's not always easy to tell looking at a colour scene what looks good in B+W, it comes from experience really.