How you control ISO is important. There is much to be said for using Auto ISO with a limited range of ISO 400 to 6400 rather than the full range, but another way of controlling ISO is to go manual, adjusting the ISO as you go from one scenario to another. It’s not a method that will suit everyone but it is a great way to learn more about light and how ISO combines with aperture and shutter speed.
Noise reduction For cleaner jpegs, use the camera’s noise reduction settings. Different levels are available, so start with standard or normal and experiment from there.
Upgrade your camera If you own an older digital camera and are unhappy with its high ISO performance, the quickest remedy is to invest in a more up-to-date camera.