Tutorial and detailed pictures here: http://www.highballblog.com/2011/10/diy-steadicam.html
My current version of a DIY steadicam. I use it with GoPro HD, Sony HX9V but can be used with a DSLR as well (you only need more weights to balance it correctly). I don't own a DSLR yet but I hope to fix this soon. :-)
In order to get the dynamic balance right, you need to hold the steadicam by the gimbal with the shaft held horizontally and then adjust the camera until you align its gravity center with the shaft.
When done right, no matter how you turn the shaft, it will remain in that position, in a neutral equilibrium state. This grants smooth footage when flying your camera with the stabilizer.
More tips on how to shoot video with a DIY glidecam here: http://www.highballblog.com/2010/06/shoot-video-with-glidecam-steadicam.html
The other three clips at the end:
DIY Glidecam First Version: vimeo.com/12828230
DIY Steadicam Footage: vimeo.com/30337132
DIY Camera Slider: vimeo.com/27821346