A good place to start with lighting is a cloudy, dull day. With even sky exposure (not near a building wall, for example), the lighting is completely flat -- even all around. Some good gun photos use just this lighting; Oscar Gaddy built a 4-light stand to mimic it. It's also called "1:1" lighting (equal left-right, top-bottom or any axis).
If you add an equal amount of light from one direction (with a properly-distanced speedlight or a blue photoflood), you'll have 2:1 lighting. This is in the range of classic, but not strongly dramatic portrait lighting. For a human portrait, a top hair light around 1.5:1 adds a nice touch. For guns, the same idea can be applied.
The advice you've gotten should get you off to a good start; then EXPERIMENT. That is really easy, and dirt-cheap with digital. And once you've used Photoshop, you'll never look back.
