For Verge staff: how do you record audio at trade shows?

I shot some video at the NAB show last year, and while the video itself was fine, the audio came out terribly. I was using a Sennheiser MKE-400 atop my GH2 (with no ability to monitor via headphones). Depending on where I was on the floor, and sometimes which direction I was facing, I would get horrible hums and hisses that sounded like interference. I'm guessing all the electrical and wireless signals around were somehow messing with my microphone and/or the cable connecting it to the camera. Add to this the sheer amount of background sound at the convention center, and I basically ended up with very little usable footage.

Verge videos from show floors always sound pristine and clear, so I was wondering if you can offer any insight into collecting clean audio in such an environment?