Cameras work by recording light and unfortunately black dogs are an absence of light which makes them difficult to capture. As you've got a DSLR you're off to a great start, you're going to need to dip into some of the settings to improve your shots. In full auto mode, the camera will examine the entire scene and choose appropriate settings to expose the entire scene correctly. The problem with this approach is that it will underexpose some areas (this is where there is not enough light) and overexpose others (too much light). I've written a bit about this sort of thing with pictures on the following page, scroll down a bit to underexposure, overexposure and the histogram:
http://forum.techpond.co.uk/viewtopic.php?f=7&t=1114Exposure compensation - as mentioned in the page above, exposure compensation is a way of adjusting the settings the camera has chosen slightly without having to choose all the settings yourself. It means you can compensate for scenes which are too dark (underexposed) or too bright (overexposed). To compensate for a dark black dog (underexposure) you need to increase your exposure which means dialling positive (+) exposure compensation. This may be available in the auto modes but may not be in which case you need to dip into the semi-automatic modes like Aperture-priority (A). In this case, if you dial in positive exposure compensation it will slow down the camera shutter so it gathers more light and therefore more detail on the black dog.
Metering is how the camera chooses a suitable exposure for the scene and by default it will try and evaluate the entire scene to try and get a balanced exposure. In some cases when you have a subject that is particularly bright or dark this won't work as it means while the general photo may be well exposed, your subject isn't which is no use. To get around this cameras offer mutiple metering modes to allow you to choose the mode that fits your scene best. Spot metering takes the exposure at just one point in the scene which would be ususally too much for a dark dog as it usually makes for an exposure which is far too slow. Instead a metering mode which gives more priority to the centre of the image (such as centre-weighted) will usually do the job fairly well, I'm being a bit vague here because there's no standard names for any of this and each camera manufacturer offers different modes and functionalities.
In both these cases you need to be aware that because you're slowing down the exposure, your picture is more likely to suffer from motion blur and also the background may end up looking a bit too bright (overexposed). As mentioned in the post above, getting a well lit day is a big help as it makes it easier to get the detail out of the black coat. You can use a flash to help you out but you have to make sure the camera compensates for the darker dog otherwise you end up with a very black dog devoid of detail. Because Alfie is a blue roan, just like Jake before him it mucks up the auto-exposure because some parts are bright and reflective whereas other parts are very dark which can give very mixed results from one moment to the next.
Shooting in raw can be a big help as well, this is sort of like a digital negative - the camera saves an exact copy of the output from the sensor but doesn't touch it allowing you to then develop it yourself. One of the main advantages of raw files is that you can make small corrections to the exposure which means you can bring some detail out of both underexposed and overexposed areas. Some cameras ship with raw developer software and some don't, the better raw developers aren't free although I can appreciate that's probably a few steps down the line for you yet.
John