These days I don’t even have to take test shots, I can see almost all the dust in the loupe and I keep repeating the cleaning until it’s gone.

Also, remember the image you see in the inspection step is “upside down” from the sensor. If there’s a dust bunny at the top of the image, it’s at the BOTTOM of the sensor.

1) Focus isn’t all that important–just set it to the closest. You don’t need to focus on the target. (This is also true if you’re setting a custom white balance, using a grey card for exposure, etc.) In fact, it’s better if the target is NOT focussed.

2) Instead of using a short shutter speed (you’re not taking a “real” photo!), use a LONG shutter speed–maybe 1/2-2 seconds. (You’ll see why in a moment.) I.e., set ISO low.

3) Overexpose by maybe 2 stops–otherwise, the white screen will look gray and dust will be harder to see.

4) Display the image. Don’t worry about the window margins, menu bar, etc.–you will be too close to see those. However, in some graphics programs, you can “present” the image so that it fills the screen.

5) Hold the camera VERY close to the screen. Don’t bother “aiming,” as you’ll see nothing but white.

6) Press the shutter and, while the shutter is open, move the camera around in a small circle (roughly). That will help ensure that any dust on the screen doesn’t show, as it won’t be in the same place during the entire exposure.

When viewing the image, zoom in and move the image around. That can help spot small dust particles or smears–they will move across your screen. What I do is to zoom in and use the horizontal scroll bar (or hold down the shift key and use the scroll wheel on my Kensington trackball) to move horizontally across the screen. I then hit page down and go back the other direction, repeating until I’ve checked the entire image.