Oh, I set up the camera on a tripod pointed at three cereal boxes. I make sure the lens is at least 50X the focal length from the target box in the center. I place the other two lenses a little closer and farther from the camera than the center box.
The center AF point overlays the middle cereal box, and since it is on a large, flat, high contrast surface we can expect very accurate AF performance.
Then I focus the camera with AF, click on live-view and take a 10X look at the boxes. If everything is dead on, the middle box will be sharp and the other two will be equally soft. I repeat a few times for consistancy.
This method has always worked well for me, and can be done even on a body without live-view by actually taking shots and reviewing on a computer. That's a lot more tedius though.
Do not review shots on the LCD after the fact. Live-view is not the same thing as the tiny jpeg thumbnail review shot.