Proper sensor cleaning is done with a lint-free cloth (like a PEC-PAD), the right cleaning fluid, and a spatula-like device. I've got those at home but hadn't brought them on my recent vacation and ran into a serious need for them. While changing lenses on my NEX-6 by the coast I got quite a bit of gunk on the sensor (probably sea-water mist condensing on the sensor which then got dust to stick) even though I was trying to be careful. Being at a remote location, there wasn't any place I could reasonably go to try to get the sensor cleaned or get the right supplies to do it myself. For stills one could do a lot of spot retouching, but as I was also using the camera for video this presented a major problem -- the camera was pretty much unusable for this. Being somewhat desperate, I decided to try cleaning the sensor with some Nikon Lens Cleaner cloths I did have with me. These are pre-moistened, individually wrapped lens cleaning cloths with a fluid that evaporates very quickly (too quickly, some people think). Being careful not to touch the sensor with my finger, I wiped it off as best I could. After two passes I could no longer visually see specks on the sensor, so I put a lens on and tried it out. The results weren't perfect, but were very much improved. So, while prevention would be best and having the proper cleaning supplies on hand would be next in line, these Nikon cleaning cloths can be used in a pinch.