You must save your digital SLR from dust. This will protect your investment and enhance your camera's life. A digital SLR is more vulnerable to dust than a compact camera, because dust can get inside it when the lens is removed. Dust may then appear on your images as specks or patches. The SLR must therefore be cleared at least once a week to avoid problems caused by dust.
Another problem is that the SLR sensor generates static electricity, which, in turn, attracts dust. The problem can become serious if you are shooting in dusty conditions, and need to change the camera lens. Dust will rush in the moment you remove the lens
You should therefore plan ahead and try to avoid changing lenses in windy or dusty conditions. The lens, for instance, can be changed in the safety of your room. However, while doing so you should be sure that you will not be using any other lens during that shoot. If there is no option and you have to change lenses in the open, try to do it in a place that is relatively free of dust.
The mirror that bounces light from the lens into the viewfinder can offer some protection from dust, though dust tends to accumulate on it too. You can use a blower brush to remove dust from inside the camera. It helps if you keep the camera facing downwards when you do it. Avoid getting the hair of the brush stuck inside the camera. You can also use a rectal syringe since it provides much more air than a blower brush.
Avoid using compressed air from a can to blow out dust from the inside of an SLR. It may expel some of the propellant in a liquid form with the air. Though this liquid evaporates quickly, it can leave a residue on the sensor.
Some dust is bound to accumulate on the image sensor, despite all your efforts to keep it clean. If you find that there is dust on the sensor, while you are on a shoot, you can try to clean it. In case you are not carrying the necessary equipment to clean it, or don't want to do it yourself, you can try using a bigger aperture to reduce its effects.
A wider aperture can make the dust less visible and give you a better image, though it will reduce the depth of field. If you use a small aperture when there is dust on the sensor, it will be apparent in the quality of the image. The dust may not be visible if there are many elements in the picture, but it will become obvious when you are shooting the sky.
If you find that you have dust on your sensor, while you are on a shoot, you can also continue to take pictures as you normally would and use image editing software on your computer to remove the specks and smudges later on.