@Exiledadmiral: Thanks very much, Sir! Yeah, basically it's all about practice, practice, practice, isn't it.

But as a general rule of thumb I think it's fair to say that when doing NMM it's never a bad idea to have stark contrasts, otherwise your faux-metallic surface just looks like any other surface. As long as the darkest bits are black and the lightest bits are white I think you're doing well. Work in many 'breaks' with surfaces like a sword or something to get the maximum contrast or if you got a large surface and don't quite know what to do with it - throw in some kind of weird angular reflection that doesn't go along any of the lines the rest of the model has. Like on the big sign thing on the Blacksmiths or the sawblades on the one guys in the Farmers team. It doesn't make much sense in terms of how light actually works, but it catches the eye. Hope that helps.

I have several different appraoches to NMM because different models call for different approaches, but I usually adhere to the above. Of course when doing a realistic model or a showcase thing I pay more attention to where I place reflections so they make a bit more sense as opposed maximum effect in a way that the light might work. Oh, and of course the very first thing when doing NMM is picking an imaginary point as light source, but that goes for any kind of miniature painting, not just NMM.