This morning I found a method to look at leaf stomata under a microscope. Here is the link to the site where I found the worksheet. Here is the procedure that we followed.
1. Paint a small area of the back of a leaf with a thick coat of clear fingernail polish (at least 1 sq. cm)
2. Allow the polish to dry.
3. Stick a piece of clear packing tape over the polished area.
4. Carefully peel off the tape and stick onto a microscope slide.
5. When viewed at 400 X the stomata and guard cells are clearly visible.