Does trying to force carbonate your homebrew seem intimidating? It really isn't that difficult. Here are a couple of techniques you can use.
When your beer has finished fermenting it's time to carbonate. You can prime in the keg and wait the required two to three weeks, or try force carbonating your beer in just a few minutes. To force carbonate the new beer, first decide how much carbonation you want.
Download the Keg Carbonation Chart and save it in your reference library:
Find the beer's temperature on the chart above. Let's assume the beer is at 36°F (2.22°C). For most beers 2.2-2.6 volumes of CO2 is normal. By using the chart you learn you'll need about 7.2 psi at 36°F (2°C) for 2.2 volumes of CO2. So for this style of beer, at this temperature you want to apply 7.2 psi (round to nearest whole number 7 psi) of pressure until the beer is saturated and won't accept any more CO2. The colder the beer is, the less pressure you need to force carbonate it.
Let's go through the process to force carbonate your beer. Your beer is cold, your CO2 tank is connected to your gas-in connection on the keg, the lid is on and sealed, and you have purged all oxygen from the keg's head space with CO2. Next, turn on the CO2 and adjust the screw on the regulator to set it for 7 psi (this will give you 2.4 vols of CO2 at 36°F (2.22°C) per chart).
You will hear gas bubbling inside the keg. It will continue for a little while and then stop. This is because the keg is standing upright and there is only a small amount of surface area for the CO2 to dissolve into. To increase the surface area, place a towel on your lap and set the keg on its side on your lap. Shaking or rolling the keg will start the flow of gas again. Eventually no matter how much you roll or shake the keg, no more carbon dioxide will go into solution and you won't hear any more bubbles in the keg. Your beer is now fully carbonated, but it's best to let the keg set inside your kegerator for a few hours to settle down before you try to dispense it. Patience young homebrewer.
Make sure you have a check valve in your gas line or beer can get into the line and regulator and ruin it. I usually disconnect the gas line from the keg, hold the quick connect against the towel and depress the pin inside the quick connect with a long slender object like a pen. All the beer in the line will shoot into the towel. Keep depressing the pin until the gas line is purged of beer. When beer does get into the line, turn off your CO2, disconnect the gray quick-connect, fill the line with cleaner to soak. I then go through the purge sequence again to get the cleaner out and then do it all over again with sanitizer. As you can see, it's best to keep beer out of the gas line to begin with by not rocking the keg too vigorously. (I'm trying to find a check valve that I can attach to the gray gas connection to prevent gas from ever getting into the line at all. When I find a good one, I'll post a link to it here.)
The colder the beer, the more CO2 it will hold. I cool my beer down to lager temperature before carbonating, around 34°F. Your beer will be full of foam from the agitation. Allow the beer to sit for a few hours and the beer will settle and dispense normally.
Another way to force carbonate your beer is to use the chart to find the correct pressure you need for the amount of carbonation you want. Keep the keg in the kegerator or fridge. Then set the pressure and forget it. The CO2 will go into solution in a few days. This is the easy way to force carbonate your beer, but it does take some time. If you shake or roll the keg every once in a while it will happen quicker. When using this method, spray a little soapy water around all the connections and the lid to make sure you don't have a leak. If you detect a leak, fix the problem before reapplying pressure. Once you lose an entire tank of CO2 in a day, you'll know why this is important.
The easiest and quickest way to force carbonate your beer is to set the regulator on 25-30 psi, connect the gas line to the cold keg, and lay the keg on your lap (on a towel because it's very cold) and roll and shake the keg for about 5-8 minutes. It is not a very accurate way of carbonating the beer, but it gets it carbonated quickly. Let the beer set for a few hours to settle and then try it. If you have a way of checking pressure inside the keg, that's even better. You have to experiment a little to get the correct amount of rolling and the right amount of time.
Once it's carbonated, set the keg back in the kegerator, set the pressure according to the chart and the temperature inside the kegerator, and forget it for a while. The CO2 inside the beer will equalize with the pressure set on your regulator. If you find you have over carbonated your beer, lower the pressure on the regulator and pull the pressure relief valve. The CO2 will come out of solution to re-pressurize the head space. By releasing the pressure frequently, the beer will lose carbonation and will equalize to the correct pressure you set on the regulator. If you under-carbonated the beer, more will go into solution until it is equalized with the pressure you set on the regulator per the chart (or if you are still in a hurry, repeat the process of purging the head space, putting 25-30 psi on the regulator and agitate the keg for a few more minutes...let it settle a couple hours and check it again).
One more note, if you plan on lowering the temperature of your keg, from 42°F say down to 34°F, add a few extra pounds of pressure first. The gas in the head space of your keg will dissolve quickly as the temperature drops and if the o-ring on you lid is not seated properly, it could leak. When you reach your desired temperature, the gas will come out of solution and escape out the leaky o-ring, leaving your beer with no carbonation. It sometimes pays dividends to give a quick spray of soapy water on all the keg fittings to make sure there are no leaks (wait till you open your kegerator one day to find two inches of beer in the bottom).