Dirt, dust, sand and grit simply don't mix well with your digital camera. They find their way over the outer surfaces of your camera with ease and can if you are not carful find their way into the inner workings where they can cause a range of issues like damage to the camera sensor which creates problems with the quality of your images or at worst they may bring your camera to a grinding halt altogether. Needless to say, but I will anyway, storing your camera in a dusty or sandy environment is not the best way to care for it.
So when you have been out at the beach or taking shots of your kids on their trail bikes, once you have returned home, use your microfiber cloth to clean off the outer surfaces well making sure you get into the nooks and crannies. The cloth will also help to remove any residual sweat and body oils which have been left by your hands. A few drops of lens cleaning solution will aid your endeavours.
If you do run into images with deteriorating quality it may well be advisable to visit the store to have the sensor checked by a professional and possibly cleaned.
If you have been using your speedlight or flash remember to clean the surfaces where the flash joins the body of your camera.