Dispensing your beer out of your own homebrew keg is one of the finest jumps in the hobby that a home brewer can make. Homebrew kegging allows greater ease than bottling, is a savings of time, and homebrew kegs often conditions your ales better than bottles do. The use of the homebrew keg (also known as a soda keg, or Cornelius keg) is quite simple, and the cost is very little compared to the convenience of serving your home brewed beer from a tap. Although the homebrew kegs are becoming rarer now that soda companies are using plastic bags in soda fountains all over the country, there is still a chance to pick them up at homebrew supply stores and online. All you need to get started with homebrew kegging is a keg or two, a CO2 tank (not strictly necessary, but quite useful) or an air pump, all the homebrew supplies used to brew you beer, and your homebrew cleaning kit.
There are a few ways to go about kegging your homebrew: forced carbonation, natural carbonation, and keg conditioned carbonation.
To use the forced carbonation method, you need to have a CO2 tank, and hook it up to your homebrew keg. Set the pressure to about 25 PSI and lay the keg down on the deck. You can easily take your foot and roll the homebrew keg slightly so that the CO2 and beer are mixed with the motion. Once the hiss of the CO2 entering the keg has stopped, you know that the mixture has reached saturation level. Now disconnect and leave the homebrew keg for about a week and a half, and it should be ready to drink. You can speed this process up by using a kegerator to keep the homebrew keg chilled during that time, in which case the beer will become carbonated quicker. Remember to turn your CO2 regulator back down to around 8 PSI for dispensing purposes, or your beer will foam for the first gallon or so! Also, it is wise to utilize the pressure release function on your homebrew keg before serving.
Natural carbonation is a technique by which the beer is put into the keg while it is still a little sweet. This way, the beer will carbonate itself! By utilizing the last bit of the fermentation process to add the much desired carbonation to the beer, you will save in CO2 costs, and you will also develop a better sense of the timing involved in home brewing and homebrew kegging.
Keg conditioned carbonation is a technique by which you wait until your beer is fully done fermenting, and then you add it to the keg with the proper ratio of corn (or priming) sugar and let the yeast do its final work. This technique also saves on CO2 costs, as well as adding a different flavor to the ale.
There are many more ways to use a Cornelius keg as well. One can, with a small modification, utilize the keg as a primary fermenter as well. The easiest way to temporarily set up a keg as a primary fermentation vessel is to remove the entire gas IN valve and tube, and then fit a length of ½ inch vinyl tubing over the fitting and the other end into an airlock. The trouble with this technique is that is can become quite difficult to properly scrub the inside of a Cornelius keg and sanitize it. This technique works much better by using the homebrew keg as a secondary fermenter.
One money saving tip that I can give you is to make your own air pump out of a spare set of fittings, surgical tube, and a bicycle pump. Simply take the IN fitting and attach a two foot piece of surgical tubing to it. Then cut a Schrader valve pout of a bicycle inner tube and use a hose clamp to hold it in the other end of the surgical tubing. These air pumps work just as well as the store bought variety, and can save you $30.
In the town where I started the practice of homebrew kegging, the guy at the brew store actually refused to sell me an air pump for my Cornelius keg! He said he wouldn't sell me for $30 dollars something I could make for myself for $5 dollars. I took his prompting and started modifying my homebrew kegging equipment immediately. Remember, ingenuity can save you a lot of money and time in this hobby. So, remember to try new methods, products, and ingredients in your beer and evolve the art of homebrewed beer.