While it sounds like it would be really easy and fun to judge a beer, the truth is it takes knowledge, practice and a trained palate in order to do it effectively. I remember the first time I acted as a steward at a beer competition and watched the judges describe the aroma, flavors, attributes and flaws and I knew right then and there I wanted to be able to do that. Fast forward 13 years and I am one of the most experienced judges in my area.
What it boils down to is really simple. Use your senses to describe the beer you have in front of you. The aroma is all about what the beer is releasing and how that impacts your nose. At times a gentle swirl of the glass can release more aromatics for you to perceive. You need to begin evaluation immediately since a sort of nasal fatigue can set in if you continue to evaluate the same sample for a very long period of time. I like to think of the aroma as the layers on an onion. The outer layers are what you perceive immediately and you keep peeling off layers until you get to the innermost core which will be much less apparent.
For appearance it is really a piece of cake. Describe the color and hue of the beer. Talk about the head, the retention, the color, any lacing. The head formation can also lead to clues about carbonation.
For flavor discuss what you perceive on you palate. In this case I like to think of a filing cabinet. What is in the front of the cabinet is what you first taste and in the final back corner of the cabinet as you go through the files is what remains in the aftertaste. Describe the flavors in full and if you cannot put your finger on a particular nuance, just describe something you know. I was once tasting a beer and candy corn came to mind since that is what it tasted like. Everyone agreed, that was the exact flavor which was present. Do I know what that is, nope, do I care, nope, you only want to convey what you perceive. Also in flavor discuss the bitterness from hops and the balance of the hops to the malt. The flavors in the finish and aftertaste should also be discussed.
For mouthfeel this is what you sense and feel. It is never a taste statement. For example you may feel carbonation, but you taste carbonic acids, you don’t feel them. Discuss the body. Often new judges are confused about the body, the best thing to do is take a particular style and train yourself to identify the body that style should have. Body is generally discussed using low, medium and high. Carbonation levels are discussed in the same terms. You can discuss if the beer is creamy on the palate or not. Note the alcohol warming sensations, especially if any are perceived and last post consumption. Astringency is discussed as well, but many judges confuse astringency. It is a sensation, not a flavor. Take a tea bag and suck on it. The puckering your tissue will have on the side of the cheek and tongue is astringency. If you don’t have that sensation, you don’t have astringency.
Then we come to the overall impression which is where you can discuss how to improve the beer and make it world-class. Most people don’t have conviction on what to put here for fear they will be wrong. What would be wrong would be trying to deduce the actual brewing process the person utilized to create the beer. If a beer needs more hop flavor to better meet style, tell the entrant the hop flavor needs to be boosted. They should have enough references today they can easily figure out how to accomplish that task without you regurgitating the time they need to add the hops into the boil to maximize hop flavor.
Lastly assign a score. This is tricky business and in the end it really doesn’t matter if you get it perfect so long as you and your fellow judge are within 3 points of each other and stay consistent with all beers being evaluated. At one time I judged low, now I believe I am pretty much on track each time I sit at the table. Judge against the guidelines, not based on personal preference. I can judge any category if provided style guidelines and have judged categories for beers I have never made.
The best thing you can do as a person evaluating beer is to evaluate LOTS of beer. Go to the store and buy at least one of every style they have. Once you have tried all those and made notes, go to another store and do the same. After several thousand beers you’ll start to discover you’re a pretty good beer judge!