Get a 1Dxx body and weathersealed lens? 
One thing you can do is go to the bathroom... And run the shower on hot water for a little bit, to get the air good and moist - and then let it settle down for a while so the air is no longer fogged and damp. Go in there and clean your gear, especially the insides and backs of lenses, filters, sensor, etc. The moistened air will grab the dust and drop to the floor (eventually). Once the insides of everything are clean, put filters in their cases, lens caps on the lenses, etc.
Regularly vacuum out your camera bag or better yet, use an air compressor and really blow it out. Wipe down your camera and all your gear with a very slightly damp microfiber cloth when you get home so it's fresh for the next outing.
Out and about there's not much you can do but the only thing you really need to worry about is the front element/filter. Everything else should keep the dust out unless you change lenses. Unfortunately, dust is a fact of life.