We've all done it. We've all used the high ISO features of our cameras. Whether we shoot with point and shoot or a high end DSLR, images will always have noise at varying levels.

WHAT IS NOISE?
All digital camera use a sensor in place of a piece of film. The sensor is made up of tiny light sensors, or objects that convert the light the camera sees into an electric charge. When light hits the sensor, electrons are produced which relay a analog signals through the camera, thus producing the image you see.

WHAT CAUSES NOISE?
Most of us know that the higher ISO we use, the more noise/grain we get. Why? Because we're increasing the sensitivity of the sensor and its photosites, it lets in alot of other electric signals which cause noise.

DSLR'S ARE BETTER THAN P&S'S
DSLR's have much bigger sensors than do point and shoots. Even within the digital slr family, there are different sizes of sensors. A crop camera body, say, a Canon 50D with a 1.6 sized crop sensor, has a smaller sensor than a full frame sensor found in a Canon 5D or Nikon D700. Larger sensors allow for larger photosites/pixels on the sensor and thus they can gather more light.

HOW TO AVOID NOISE IN THE FIRST PLACE
#1: Use the lowest ISO possible
There are a few ways to avoid noise in your images. First off, use the lowest ISO that your camera settings will allow. I see alot of people use a high ISO when they shouldn't be. You do not need a 1/4000th of a second shutter speed to photograph a moose. You do not need a 1/8000th of a second shutter speed to photograph a running baseball player. For most sports, a shutter speed as high as 1/800th will suffice most of the time in decent light (and that's generous).

#2: Use a tripod or IS/VR
By using a tripod or the IS/VR found in body or on many camera lenses, you will be able to use a slower shutter speed and thus a lower ISO. It seems like common sense but at some point or another, alot of us like to think we can rely on high ISO and be lazy. If you don't have a tripod now, use a solid surface. Buy a tripod. Even a cheap tripod is better than no tripod.

#3: Many cameras come with in-body noise reduction. I say use it unless you have a program on your computer that will allow you to reduce noise in post production.If you plan on reducing your noise later, TURN OFF the in camera noise reduction. I have found that noise reduction in camera softens my images, leaving me permanately with images I can't fix.

#4: Keep you camera in a cool environment as much as possible.
Heat increases noise in camera. I'm sure there is alot of info about this online, but I'm not going to go into it. Just remember, cool is better.

#5: Long exposure also increases noise. It depends on your camera, but some cameras see some noise at exposures as short as a few seconds.

#6: Do not underexpose your images. When you underexpose an image and have brighten it in post processing, noise will appear fast in the dark areas. No bueno. Nail your exposure when the shot is taken. I recommend anyone that doesn't know about or use their histogram check out this article [link] .

Sometimes, in order to get the shot, noise will be inevitable. Either you need a long exposure to get a moonlit shot, or you need to photograph something moving quickly in a dark building. Use a high ISO when you must. EXPOSURE IS KEY!

POST SHOT NOISE REDUCTION
After following the above steps, many times you'll see noise in an image. Sometimes is ok, sometimes its not. For those times when you need to get rid of noise, you can try some programs available to buy that help out alot!

I use Noise Ninja. [link] The Photoshop Noise Reduction filter will work as well, although it does have its flaws. By using Noise Ninja, or another plug-in, the photographer has the option to selectively reduce noise, unlike using the in camera reducer.

To selectively use it, I copy my later (Ctrl or Apple + J) and then apply the amount of reduction that I want on one certain area. Once achieved, I use the layer mask to get rid of the reduction on the rest of the image. Then I repeat as many times as necessary on the image. Noise reduction softens the image, so its good in some spots and bad in others- You'll have to be the judge. Some areas need to remain critically sharp, even if this means a little bit of noise. For example, sometimes, there is no point in having a blurry background with noise. Use some reduction on the backgroud to clean up the image. This technique also works on selectively sharpening your images using the Unsharp Mask.

DO WHAT WORKS FOR YOU.
There is lots of info on the net about noise reduction. There are lots of programs as well to plug into Photoshop to reduce noise. Do what works for you. If you need help, GOOGLE something like "noise reduction photography tips" or "noise reduction software."

IF ANYONE HAS ANY OTHER SUGGESTIONS ON THINGS THAT WORK FOR THEM, FEEL FREE TO PUT IT IN THE COMMENTS FOR OTHERS TO READ. LIKE I SAID, THERE'S MORE THAN ONE WAY TO SKIN A CAT. (although I've never actually skinned a cat, so who knows? )

Cheers everyone