You have to start wiht printing/drawing this on some paperboard (you can also make a 1st version on normal paper, just to adjust its shape for your camera):
Next, you need to cut it out, and run down on the lines with sharp edge of scissors, so you can fold it without any problem. After that, you must apply a layer of glue and lay a tinfoil on it (it's for better reflecting of light, so brushed side goes on the glue).
Wait until glue is dry, fold it by the lines, and wrap it around with duct tape.
Lines on the picture that makes something like \__/ (on the upper part) are a part of 'exit' for light. Next step is to take a pice of white paper and stick it (you can see that on the lower picture).
I modified this diffuser a little to make it fit for my camera and that is last and the bestversion (sorry for quality etc, but it was taken with my mobile phone):
As you can see, I cut out a hole for my flash. You must make few versions to make it the best for your camera, the most important is where you have your flash. The white paper ath the end should be pointed at place in front of lens, where will be object that you want to photograph.
And now a little comparision. On the left without, on the right with diffuser. You can see difference ;)
If you have any question, put it in comment, I will answer next time. Also, next time- I'll show you more of my animals.