Why the wet leaf and not the dry
Dry leaf has been shaped, compressed and sorted, and shape conceals as much as it shows: a tight pellet, a flat blade and a twisted strip all look like decisions about appearance. Steep the tea and the leaf unrolls back towards what it was when it entered the factory, and the marks left by every operation become visible at once. You can see how much of the shoot was picked, whether it was cut or twisted, where it oxidised, whether it was scorched, whether it was pressed. None of this requires equipment. Tip the spent leaf into a shallow dish, spread it out, and look at it in daylight.
What the plucking standard looks like
Start by finding intact shoots and counting. A bud with one leaf, a bud with two, or open leaf with a length of stem and no bud — these are categorically different intakes and they set a ceiling on everything downstream. A fine green tea should show small, uniform bud-and-leaf sets; an oolong should show open shoots with stem attached, because that is what the process needs and not a sign of carelessness; a volume black tea will show a mixture that no hand plucker would have produced. Uniformity is as informative as the standard itself. A wet leaf containing both tender sets and coarse mature leaf is telling you the intake was mixed, which means part of the batch was over-processed and part under-processed however well each operation was run.
What rupture and shaping look like
Twisted leaf comes apart into recognisable leaf. Cut leaf does not — CTC granules unroll into small angular fragments with cut edges, which is why they give everything up in ninety seconds. Rolled-ball oolong opens into large, thick, largely intact leaves that were compacted rather than torn, and a good one will still be opening after several infusions. Look for the shape of the damage as well as its extent: a leaf ruptured evenly across its surface went through a roller, and a leaf with a bruised margin and an intact centre went through a shaking drum. That last observation is worth practising, because it is the direct physical evidence for the claim that oolong is oxidised at its edges rather than half-oxidised throughout, and it is visible in almost any decent oolong.
What the heat left behind
Colour is the main record. A well-fixed green tea gives a wet leaf that is uniformly olive to bright green; patches of red or brown at the stem or on individual leaves mean part of the batch kept oxidising after the rest had stopped, which is the commonest fault in the category and points either at an uneven fixation or at leaf that heated in transit. A yellow tea's wet leaf is a soft yellow-olive throughout, which is the direct evidence of the smothering step. An over-fired tea shows scorched edges or a dull, flattened brown. A heavily roasted oolong opens dark and can look burnt while the liquor is sweet, which is the one case where the wet leaf will mislead you if you read it alone.
The tail: stalk, stem, flowers and compression
Finish by looking at what is in the dish that is not leaf. Stalk in a strip oolong means nobody paid for the hand picking, which is one of the largest labour costs in the category. Stem in a Japanese tea is not a fault at all if the tea is a kukicha, and is a refining shortfall if it is not. Dried flowers in a jasmine tea usually mean decoration rather than scenting, because traditional practice screens the spent blossom out after every round. And leaf from a pressed cake carries physical evidence of the press: compacted, sometimes folded, occasionally with fragments that never fully open. Each of these is a specific claim about a specific step, checkable at a kitchen table, and worth more than the entire back of most packets.