Okay folks, how do I shoot b&w with a Nikon D70? I upgraded from Nikon 5700 and on that one I just hit a button.

You will have much more control over the image in photoshop, and will come out with a higher quality B&W. Besides, you'll feel like a fool if you take a B&W image you eventually want in color, or accidentally leave B&W enabled for a color series.