Very easy to do, here are the steps:
1 Make two pictures, appr. 63mm horizontally apart, like your eyes are. You can use any camera, make a pinhole-box, or use a special one like the Iloca above.
2 Crop and align them with Picasa (or your own photoshop-thinghy). You have to think a bit: the left picture has to be at the left - my pinhole-print is wrong, you will never see 3D there!
3 Size: I print on 10x15 cm. If you only want them on your srcreen, the distance has to be 63 mm again.
4 A dark background is better for easy viewing.
5 How to look at them: it's a technique, or a trick. First: relax. Eyes at infinite, then just concentrate on the middle. Or buy a viewer like my Underwood, patented in 1901.
Try it! Download one of my pics above, find the right size for your screen and practise, get those eye-muscles moving. It's fun.
7 Sep Update: just a small hand-held quicky. I moved the camera not only horizontally, but also in a circle (more or less...) and discovered the 3D effect does nòt get better, but rather "well-done" (and I prefer mine "rare"):
And if you can get antique stereoscopic cards - those are real time machines! Great to be in that street, a century ore more ago:
Oh - I always forget the anaglyph method, because I don't have, nor like, the glasses. But that's also rather easy to do:
And of course: