http://www.youtube.com/watch?v=STeFgjuqCUY
Make sure the two pencils or markers you use for this method will work with the particular anaglyph glasses provided. You can determine this by just drawing a streak of the color with the marker/pencil and looking at it through the glasses. If it is red and you just look at it with the red lens, does it disappear or almost totally disappear? If so, that will work. Do the same with the blue or cyan lens and marker. Once you get two markers that will work with your glasses, you are good to go. See the video above for the technique. Of course, if you use Photoshop to do your drawings, you can experiment with the colors using its color controls to get just the right shade of red / cyan to work with your glasses.