Care for the Digital Sensor
The digital sensor in your camera is your camera's "film". In the point and shoot cameras, the sensor is smaller and is usually sealed within the unit - which is a good thing. The sensor in the DSLR camera is located behind the mirror which is right behind the lens. When the lens is removed from the DSLR, the unit is no longer "sealed" and dust can make its way into the camera. It will eventually find its way to the electronic sensor and the static will draw it like a magnet to the sensor's surface.
One of the best tips I learned when the lenses are being changed, is to keep the face of the camera pointed down. This avoids any additional dust falling into the camera body, and if there happens to be any in there, hopefully it will fall out. Being outside in the wind is not a place I would ever change a lens - even if I kept it face down. It is just too risky.
It is recommended to always have your sensor cleaned by the manufacturer. The only cleaning that most manufacturers will allow the owner to use themselves is a bulb blower. NEVER USE CANNED AIR on your sensor.
There are several products that have been designed to clean digital sensors, and if you have the knowledge and nerve it can be successfully accomplished. What you are cleaning isn't actually the sensor itself but a filter that is covering the sensor. You must keep in mind that damaging your sensor is rendering your camera useless and it will be very expensive to repair.
The link below has detailed instructions for all the different cleaning methods for a digital sensor. They recommend that you read every page on the website before attempting any kind of cleaning. And if you are nervous at all about it, have a professional clean it. Cleaning Digital Cameras Demystifying D-SLR Sensor Cleaning.