How can I get my images to show more detail with the threshold tool?

I have Photoshop 7.0 first of all. I usually create most of my graphics with the aid of the threshold (image adjustment) tool. My problem is that I can never seem to get the details from the picture that I would like to show up to show up. Usually I end up with too much shadow or too much lightness in the picture to make out any kind of details. I have scoured the internet, but I have not been able to find a tutorial or guide to prep my images before I use the threshold tool. Does anybody know of a way to get a better result?
Thanks!