I live in rural Iowa and drive a great deal on gravel roads and photograph in dry, dust filled environments. I have cut way down on dust problems by following the same basic procedure outlined by Ronald Moravec in post 6. The key is to create as many barriers between the film and dust as is practicable.
I would add to Ronald's post that static electricity is your enemy. When I clean both sides of the dark slides in the darkroom, I use an anti-static cloth. In the field, I again wipe the film holder with the anti-static cloth before it goes into the camera. I try to pull the dark slide out slowly and evenly to cut down on static build up. If there is dust floating inside your camera, pulling out the slide can create a charge which will attract the dust to the film. Gravity works and the dust will usually end up in the sky portion of the negative (which is toward the bottom of the film when in camera). Also, I use a 3M vacuum designed for vacuuming out photocopiers. The vacuum has a special filter to trap all but the most microscopic dust. I found one cheap on the auction site. If using a regular vacuum, do so in one room and load the film in another. You can also make sure the power unit of the vacuum is away from the camera or film holders if using a regular vacuum.
I know it sound anal to go through all of this. It is worth the few extra minutes spent vacuuming and wiping when loading film as opposed to having to spot each print. Personally, I hate spotting prints.