Check out this discussion of carbonation and the accompanying chart: http://www.kegerators.com/articles/carbonation-table-pressure-chart.php I've found the chart to be very helpful. As others have said there is more than one way to force carbonate. I use the set-n-forget method. Using the chart, I set the pressure based on the desired level of carbonation and temperature of the beer, then leave the keg sit for 7-10 days. I sometimes give it some shaking when I first connect the gas to get things going a little quicker. I serve at the same pressure used to carbonate. I have a few different lengths of serving line that balance my system for good pours at different pressures.