The Perceptions score comes from comparing what you found in each beer to what the Proctors found, and also the expectations of the style guideline. Start with major flaws and features, and assign levels to everything you mention, using Descriptive and evocative words like bold, aggressive, blinding, faint, muted, delicate, juicy, rich, etc., that bring that Appearance, Aroma, Flavor or Mouthfeel to life for the graders that are not tasting it. Avoid generic words such as nice, good, some, very, back-bone, upfront, etc. So, “Aggressive & sweet “juicy” tangerine hop dominates a medium, neutral malt with faint bready background note” is far better than “good citrus hops and nice malt backbone.”
If something expected in the style is missing or wrong, mention it. “Lacks the banana ester/clove phenol expected in a hefe.” Or, “has banana ester/clove phenol that is incorrect for an American wheat.”
Basic 3×5 index cards are roughly the same size and space as the Aroma and Flavor sections of a score sheet. A simple practice method is writing down your Aroma and Flavor Perceptions and Descriptions on index cards while you’re drinking beers. Later, grade your own efforts by verifying all Cue words are covered, and evaluate how well you described the beer. Have other people read the card and tell you if they “get” that beer based on your description.