The shake and guess method simply means you are lifting a keg up, shaking it, and trying to approximate how much is in the keg, and then entering via point-count method (i.e. 0.6 kegs). Not a very reliable method, to say the least.
The condensation method involves leaving the beer cooler door open long enough so that the air inside the cooler warms up and condensation starts to form on the keg, which causes a line to form where the level of the beer is at. Theoretically, that is. I’ve seen this method work, and I’ve seen it bomb as managers squinted to find the condensation line. In the end, it’s a lame method and not recommended.
Weighing kegs is a very accurate method for determining how much is left inside the keg. Though labor-intensive, it is leaps and bounds more effective than the first two methods. Simply place the keg on the scale, enter the pounds into Bar Patrol App and the system knows how much is left in the keg based on the full and empty weight of the keg (which we have for your at the bottom of this page.
Draft meters are highly accurate and eliminate the need to lift kegs on to scales. The only problem is, it can get very expensive. One decent draft meter can cost $150 – $200 per keg. If you have a lot of handles, that can add up in a hurry. However, if you can afford to have them, they are highly effective.