A camera
Preferably a DSLR because you are going to shoot under low-light condition, if not, just use a compact camera. Compact camera users are advised to shoot outdoor with the help of a bit of sunlight (NOT direct sunlight).
I used both DSLR camera Canon EOS 450D and compact camera Panasonic Lumix FX10 for this tutorial.

A white background
This could be a large paper, cardboard, cloth or as long as it is white in colour. I am using a 1mm thick cardboard, cost less than US$1.

A subject (your figure)
The size of your subject depends on the size of the white background you have. Larger background for larger figure. My background size is B4.

A tripod
Mount your camera to a tripod if possible to prevent hand-shake. Image Stablizer has its limit when shooting under low light condition as the shutter speed will be slow. Forget about using high ISO to increase your shutter speed, stick to ISO 100/200 even if your room is dim. The reason is to minimize 'noise'.

A secondary white light (optional, for white subject on white background)
You will need this if your room is not properly lit. The point of using a secondary light is to overexpose the background. Read until the end for explaination.

A photo editing software
In this tutorial, Adobe Photoshop CS is used.

Now that you have gotten your tools ready, it's time to shot! My subject is a 100mm tall Nendoroid Asahina Mikuru Bunny version of anime "Suzumiya Haruhi no Yuutsu" as below. The secondary light is NOT used for this figure.

Above: Nendoroid Mikuru, Canon EOS 450D DSLR, white cardboard and a secondary light. Simple setup, more than enough :)

Once you have gotten your subject focused, shoot. For my room lighting condition, which is quite dim, I increased the exposure level to EV+1 on both my DSLR and compact camera.

Photoshop It!
Transfer your photo to a computer for editing. You may not need to edit your photo if the background turns out pure white the moment you shoot it, but that is very less likely the case with this kind of setup.

In Photoshop, click on the Eyedropper Tool. The Color Picker window will pop up with some R.G.B values (if the R.G.B values show 255, it means pure white for your information). While selecting the Eyedropper Tool, right click and hold it on your figure photo. Move around with it on the white area only (not your figure, and not the shadow of your figure) of your photo especially the edges and you will see the R.G.B values change in real time. Memorize the lowest R or G or B value. In my case, 233 is the lowest for all R.G.B, found on the bottom-right of my photo. You might get different values for R.G.B but only memorize the lowest value because we are going to level it up to 255 in the next final step.

Above: Find the lowest R.G.B value using Eyedropper Tool on white area only.

Once you get the lowest R.G.B value, go to Image > Adjustments > Levels (or CTRL-L) to pop up the Levels window. Modify the highlighted value from 255 to your lowest R.G.B value (233 in my case) and...... PRESTO! A pure white background figure shot! Congratulations!

Above: The Levels window.

Here's the results with my DSLR, before and after adjustment.

Above: Before asjustment. Right click and save the picture if you just want to play around with Photoshop.

Above: After adjustment., pure white background.

A compact camera will not give as much photo details as that of a DSLR camera (shown below) but the method still works to achieve pure white background. Shooting outdoor might help. Shown below is a photo taken using compact camera Panasonic Lumix FX10.

Above: Before adjusement	Above: After adjustment

White Subject with Pure White Background Photography.
Now, what if you have a white figure as your subject? Adjusting the Levels in Photoshop will make your white subject loses lots of detail.

Therefore, in this case, the secondary white light comes in and plays an important role (to achieve about 1.5 stop difference between foreground and background to overexpose the background automatically). Brighten up ONLY your background after focusing the figure using your camera. See below picture for setup. I was shooting Pearl Black version "Ryomou Shimei" from anime "Ikkitousen".

Above: Shooting a white subject with pure background.

Above: Pure white background. Sexy Ryomou Shimei! (click to enlarge)