With the aid of Google translation and the German-English dictionary at (and some commonsense 
), here's the test recommended by Canon Germany for assessing whether your 10D has the infamous focus problem, taken from an article on the German site, . I've done my best to get an accurate explanation out of the translation, but no guarantees.
Use a target such as a magazine page fixed to a wall. The target should be flat and well-lit. The camera should be set to maximum aperture and the first picture taken using autofocus. I assume this means using either manual or Av mode. Nothing is said about focus points.
For the second picture, set the camera to manual focus mode. You must ensure the dioptre setting is correct for your eyesight. Focus manually, using your judgement to determine optimum focus and not the green in-focus indicator in the viewfinder.
Open both pictures in your favourite editor and compare the pictures at 100%. If there is a clear difference in sharpness in favour of the manually focussed picture, Canon will, says the article, make the requisite adjustment to the camera and, if necessary the lens.
Another test method can be found in this article, Focus Testing, by Bob Atkins. Pekka Saarinen's excellent forum post is also worth reading.
One comment, made by someone who read this page, asked "how can you make dioptre adjustments, if focus is not accurate?". I did some googling to see what advice was around. I couldn't find anything that seemed definitive (if anyone has a good reference, please let me know), but this is my summary of what I found and what I did to check my own settings. It seems that the best method may be to do this adjustment without a lens on the camera. The purpose of dioptre adjustment is to ensure that your eye is accurately focused on the focus screen*, so an image is not needed, you can use the focus point markings as a guide
I recommend setting the camera on a tripod: the adjustment wheel is quite stiff and awkward to turn and the consequent camera movement makes it harder to keep your eye focused on the markings. I also used the plastic, translucent lid from a well-known snack product to help diffuse the light. This not only aids help the view, but is a little protection against dust while you have the camera body open.