If you have a dark dog you've probably already experienced the frustration of trying to take pictures that don't have your dog looking like a big black blob...
Most cameras, even "point-n-shoot" have a button/option on them for exposure compensation. It's usually a little +/- symbol of some sort.
Your dog comes out black because the camera's light meter takes in all of the light over the whole frame and decides how to take the picture. Your dog is dark, but the camera uses an average so unless it is a closeup the picture will probably come out under exposed.
You want to tell the camera to let in more light than what it wants to; so you'll go + a few stops. You will definitely have to experiment.
You may also want to tun on the camera's fill flash, which is used for helping to compensate for back lit subjects but can also be used for this purpose.
Inside me is a thin woman trying to get out. I usually shut the bitch up with a martini.