Way back when yer ole Marlton Mom was in skool I had the best idea for a photogram and it made me the teachers pet.
First I want you to think of a scene in layers, with a background layer, middle layer and then top layer. (You can use as many layers as you want, it doesn't have to be 3)
Keeping in mind that the photo paper that is uncovered the longest will be black and the the parts of the paper that are covered up the longest will be white set up a layered scene where you can remove elements at various time intervals to get shades of gray.
The trick here will be in composing a scene that will allow you to remove the elements from the top layer with out disturbing the lower layers so they keep their spot and don't move.
Hopefully you get the idea.
I composed a Ski scene with mountains and a cross country skier that I cut out of a magazine. The skier was white and the mountains were various shades of gray and the sky was black.
Then just for kicks I used the finished photogram as a negative and reversed the exposure.
The key here is composing a layered scene and removing the elements as you continue to expose the paper. I started and stopped the light, I didn't try to reach in and grab.
Now with the invention of the interwebs and Google you have a bevy of images to clip out for your subject.
Go Crazy!
Signed,
Yer Ole Marlton Mom