There are three schemes that I usually try for, in increasing order of difficulty.
1. (url="http://"http://homepage.mac.com/weepul/smoothfreighter.jpg")Example(/url). Cookie-cutter, I might as well call it. The key light is the main, bright "sun" light (you got your terms mixed up, Azdara :p). I usually make it fairly strong (often over 100%), either white or slightly tinted yellow or whatever color would work well, and directed at an angle from behind the ship. The goal of the key light is to provide the strong light source as well as accentuating features on the ship - shadows, and, most importantly, specularity. The highlights on whatever surface your ship has are what really defines what the material looks like, so a somewhat glancing key light is good for showing it off.
Then, I'll usually use two fill lights - somewhat dim, colored lights to let you see in the shadows of the ship and to approximate environmental lighting (assuming the ship is near a planet, in a nebula, etc.) I personally like blue, but that's just me - I like the color blue. 
I'll often have one coming from below the camera, and another from the side, a bit more toward the camera than straight off to the side of the ship. Either that, or both lights will form about a 100° angle between them, with the camera mostly in the middle. There's no particular science here, though - just play around with the lights until they illuminate the ship nicely, hopefully picking out some more details.
Since fill lights can look odd with hard, raytraced shadows, what I sometimes do (when I'm not using area lights in LightWave) is turn down the shadow opacity - or, if your program doesn't have that option (Infini-D, which I used to use, doesn't) I'll duplicate the light, make the two copies' brightnesses add to the desired value, and set one to cast shadows and the other to not. That way, there will still be visible shadows, but dim illumination will carry through and keep black, shadowy pits where you can't see anything from forming. It also keeps some variations in shading that "ambient light" utterly lacks.
I always used "distant" lights, not point lights or spotlights. That way, I could direct them simply with rotation, not having to worry about their position. Any of those would work.
2. Scheme #1 looks decent, and it's fast, without requiring too much thought. It gets somewhat boring after a while. #2 is essentially just making a similar scheme (key, possibly a second bright light, and fills) but not following the key-from-behind-add-fills scheme. Do something more creative - something that fits into a scene better, a scene that doesn't just show off the ship but is a full scene. (Um, I don't have an example.)
3. (url="http://"http://homepage.mac.com/weepul/weepbatscene.jpg")Example(/url) (ship by Captain Skyblade). The realistic approach. Figure out where light sources would be in the scene, and stick lights there. Engines, explosions, the sun, planets, a brightly-painted station and its lights - they are all fair game. The trick here is to keep everything arranged such that you can see them with the camera and form a good composition, and still have a good lighting setup. "Fill lights" just for the sake of adding light can be used, but only carefully - light just for the sake of light is sometimes needed and beneficial, but not "realistic", which is the goal here.
Keep in mind, guidelines are just that - schemes to guide you. They aren't rules. The only rule is that you should think the final image looks good.
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