Hey..
Use various informative stuff such as Nikon expert lens recommendation blogs, articles, Nikon d40 Manual for lens recommendation and other mode settings for your black model photography. Here are some tips that i want to share with you that gives you better result:
Get your settings sorted before you start
Use a wide-angle lens
Don’t touch the zoom!
Get the focus right
Shoot in RAW, with black-and-white preview
Look for the light and shadows
Look at the foreground AND the background of the shot
Don’t over-process your images