Below is a 3-D picture pair I took in my yard.
Many people have a tough time doing this, but when it
works...it's very cool !!! Without any tools, you should see an
image which looks as though it came out of a viewmaster.
To see in 3-D look between the two photos (15-18 inches
away works best for me), cross your eyes and try to make a solid third
photo. If you see 4 pictures when you cross your eyes, you've crossed
them a bit too much, uncross them a bit and the 2 inner pictures should
merge. When they merge, you should be able to see a 3-D image on the center photo
(it takes a moment to focus).