Don't be afraid to crush your blacks, but don't clip your highlights. Film, especially black and white, has real 100% black, but an incredible highlight tail. This will produce the most a natural image with striking contrast. Depending on the project, try and use shadows as graphic elements in your frame. And don't be afraid of subtlety. Not every shot has to be a melodramatic Sin City still frame--low contrast B&W can be as immersive and powerful as high-contrast. Just remember, even in a low-contrast scene, to include one very bright element and one very dark element to give the viewer a sense of relative contrast within the other tones. If you do a straight desaturation, you're working with luminance information only, which makes your lighting absolutely critical. You'll probably want to use harder light than you're used to, or the image will feel a little "undefined." Let me know if I can offer any other pointers. B&W is something of a passion for me. As usual, the best research is to go watch some great B&W movies and steal like an artist.