Okay, so you've brewed your first batch of beer and taken your first step into a new world of possibilities. Well, either that, or you just liked it and want to do it some more. However, brewing with nothing but malt extracts, hops and yeast will very likely begin to bore you after awhile. Browsing through recipes, you will undoubtedly come across many which utilize various other ingredients to give them unique characteristics. Probably the first and most common of these which you will encounter will be specialty grains.
Specialty grains are generally used to add color and flavor to your beer. Some can also add body or various aromatic elements. All of these aspects of your beer, while perhaps too subtle to be noticed individually by most people, can combine to increase the overall enjoyment of your beer as a whole.
Since most of these grains are not mashed, they will not add any fermentable sugars to your wort. Thus, the addition of a pound of grains to your recipe does not mean you should omit a pound of malt extract in return. There are a variety of grains available to the homebrewer, the most common of which I will outline and describe here.
Crystal malt: Probably the most common variety of malt in use, crystal malt is the only grain we'll be discussing here that is mashed and thus does contain fermentable sugars. However, the mashing process used for crystal malt differs from that used to produce malt extracts, and not all of the starches are converted to fermentable sugars. As a result, it will only add a relatively small amount of sugars to your wort, so you still should not reduce the amount of extracts you use. Crystal malt comes in a wide range of colors, which are measured in degrees Lovibond. The higher the number, the darker the malt, so 10 or 20 is quite light, while amber ranges around 30 to 50, and anything above 80 is quite dark.
Chocolate malt: The term "chocolate" here refers to the color of the malt, which is a deep, rich brown, and its aromatic characteristics, which mingle bitterness with sweetness. These traits are produced by roasting malted barley for a certain length of time.
Black Patent malt: Like chocolate malt, black patent is also made by roasting malted barley. However, black patent is roasted at significantly higher temperatures. This causes the oils which normally produce malt's aromatic character to evaporate. As a result, black patent is used primarily to add color to a beer. Larger amounts will also contribute a malty bitterness to the beer which is markedly different from the bitterness of hops. To understand the difference, sample a nice smooth stout such as Guinness, and then sample an IPA. The subtler bitterness perceived in the stout is mostly derived from malt, while the spicier, more assertive bitterness of the IPA comes entirely from hops.
Roasted Barley: Roasted barley is subjected to even higher temperatures than black patent malt, and is not malted beforehand. As a result, it provides little to no sweetness, but does add a very distinct flavor and aroma to the beer, not unlike roasted coffee beans. Many stouts have borne a coffee-like flavor and aroma since long before it became fashionable to add actual coffee to the brewing process. These characteristics were imparted by roasted barley. Be aware that roasted barley will also have a dramatic impact on the color of your beer and its head. I once added less than a pound to a batch of red ale, and wound up with a batch of black ale (it was good, though). If you're not brewing a porter or stout, you should take care to use roasted barley sparingly.
Oats: Another common grain used in the brewing of stouts, rolled or flaked oats (not oatmeal) will add a unique flavor to your beer. The more glutinous nature of oats will also impart a silky sort of thickness to your beer's body. Oats, unless you roast them, won't have much of an effect on the color of your beer. Again, use sparingly - half a pound of oats added to a batch of stout will alter its character significantly. More than a pound may result in a beer that borders on the unpleasant for all but a small niche of stout drinkers.
Toasted Malt: In some beer recipes, most often pale ales and lagers, you may see reference to "toasted malt". This is very different from roasted barley. Usually the toasting of malt is a step you will perform yourself at home. Simply spread the grains out in a thin layer on a cookie sheet and toast them for 4-8 minutes in a toaster oven or under a broiler. Watch them closely during this process - if the grains begin to brown, burn or change color, remove them immediately. To reduce the possibility of burning, it is best to toast whole (that is, uncracked) grains, and then crack them afterwards. Toasting is most usually done with lighter crystal malts, but can be done with the darker varieties also. It will impart a subtly rounded flavor and a slightly fuller body to the finished beer.
In order to use any of these grains in your beer, they will first need to be cracked. Your local homebrew shop will be happy to crack them for you when you purchase them, or if you have a grain mill you can crack them yourself - just remember, they only need to be lightly cracked open, not crushed or ground. If you don't have a grain mill, you can spread out the grains in a thin layer and gently but firmly go over them with a rolling pin.
There are a couple of ways to introduce these grains into your wort. One is simply to dump them in at the beginning of the boil and let them cook away. You strain your cooled wort on its way into the carboy anyway, so most of the grain husks will get filtered out. This method presents two primary disadvantages. First, it will significantly lengthen the time it takes you to get your cooled wort into the carboy - your strainer will be clogging constantly, and you'll have to empty it a lot more often. Second, boiling these grains along with your wort will cause a lot of starches and particles to remain in your beer. Most of these are too small to settle to the bottom, especially in the midst of all the commotion that primary fermentation causes, and your beer will be noticeably hazier or cloudier.
The other more commonly used method of utilizing these grains is by first steeping them and then sparging them into your brewpot. You will need a brewing thermometer in order to do this. To steep the grains, dump them into a pot with a gallon or so of cold water. The next step will be easier if you don't use your brewpot for this - any soup kettle or stockpot of sufficient size will work fine. If you're using a lot of grains, you can add another half-gallon of water, but one gallon is generally sufficient. Stir the grains around with a wooden spoon to make sure they all get soaked, then turn the burner on medium. Stirring occasionally, wait until the temperature gets between 170 and 180 degrees Fahrenheit, then turn off the flame and cover the pot tightly. If you can't cover the pot, you may need to leave the heat on low to maintain this temperature. Now, let the grains steep for about 15 minutes.
This next step is called sparging, and for it you will need a strainer and another gallon of water. Pour the liquid from your steeping pot through your strainer and into your brewpot, leaving the grains where they are. Once most of the liquid is gone, fill the strainer with grains and hold it over your brewpot, then slowly pour some water on top of these grains. What you're doing here is "rinsing" the grains in a sense, getting as much flavor, color and aroma out of them as you can. After you sparge each "load" of grains, press down on them firmly with your wooden spoon to squeeze out a little bit more, then discard the grains. Repeat this process until all the grains are sparged, and you should have two gallons of water in your brewpot. Simply boil it and cook your wort from there.
As a side note, spent grains make an excellent mulch for you gardeners out there. However, you should be very careful never to use as mulch a mixture which may include hops, or which has come in contact with them. Hop resins contain chemicals which are highly toxic to dogs, and can cause serious injury or death.
That about covers the use of specialty grains. Note that this is markedly different from all-grain or all-malt brewing, an advanced method of brewing which eliminates the use of malt extracts entirely and requires the homebrewer to go through the mashing process himself. This adds a vast amount of complexity to the process, and should only be considered by very experienced and dedicated homebrewers. I myself have brewed dozens of batches of beer over the last six years or so, and have never tried all-grain brewing. If someone out there with experience wants to write a primer or curriculum on this subject, I'd be happy to link to it, but I'd rather not write-up something with which I have no practical experience.