If you want to do it faster and maybe more accurate you can find one of those tables spoken of. If you know how many "Volumes of CO2" a certain style has then use that information along with the temperature of your beer to figure out what psi to set your gauge at. An example is, on my Oktoberfest they want 2.5 volumes of CO2. I had my beer at 40 degrees so I looked at the table and it said 12 psi. I set it at 12 and started to rock my keg back and forth holding it at the bottom with my feet. You rock it until you don't hear anymore CO2 going in. Now when you hook up your CO2 be sure and connect it to the OUT side of your keg. This way it will bubble up from the bottom. Now if you do it this way you can immediately enjoy a beer. I store it at 40 degrees and 12 psi to maintain head. When I serve I usually drop the pressure to 8 or so psi. I repressurize when finished serving.
Now, you must rock the keg for around 15 minutes. If you want to speed up the process you can put it at 25 psi and rock it for 5 minutes. Stop and reset the tank to 12 and continue. This usually cuts the time in half. Just don't go too long or you'll get too much carbonation. If you ever do over carbonate just bleed the pressure off and it will come out of solution. May take a couple of days depending on how bad it was.
The difference between ignorance and stupidity is that you can fix ignorance... if you're not stupid!