I've graded many BJCP exams, and here's my advice for the tasting portion. The scoresheet gives crucial hints. In the "aroma" section for example, the scoresheet says "comment of malt, hops, esters, and other aromatics". It's important to hit all those features, even if you don't detect them (no diacetyl, no DMS). Similar hints are part of every section - hit all these highlights! I'm amazed at how many scoresheets make no mention of hop bitterness levels, etc. Another suggestion is to use as much descriptive terminology as possible. To (correctly) state that a beer has medium to high malt flavor is good. To describe (again, correctly) that the malt flavor is bready, or toasty, biscuity, caramel, roasty, etc. is MUCH better. Oh, and don't forget to check the boxes on the stylistic accuracy table at the bottom of the scoresheet! Cheers, and good luck on the exam!