The helmet Mike uses for his act is an awesome, 1970s vintage Canadian motorcycle helmet that he's modified heavily. And by modified heavily, I mean he's put a bunch of spikes on top.
Knowing that I wanted a 3/4 view of the helmet, I set up a softbox camera left, pointed slightly down. This provided the majority of the illumination and also gave the helmet a bit of shadow around the edges to provide depth. A second light bounced off a reflector to the right of the helmet ensured the shadows weren't too harsh.
Not a bad shot, but hardly slick enough for my purposes. Only having two lights means that I often have to plan my post-production pretty carefully – what I could accomplish with three lights, I do with two and Photoshop. So for the next shot, I put the second light with a slave trigger inside the helmet, taped to the top. You can see how this gave the inside of the helmet a great glow:
Here's the a quick back and forth of the two images showing the difference:
With the shoot done, I then proceeded to process and edit the shots. A little bit of masking and editing in Photoshop resulted in this next image. I composited the glowing interior with the exterior shot, brought in a new chin-strap and did some cosmetic retouching.
And now the final result. I removed the background, brought out some highlights and tweaked the Levels on the spikes.