Pokédex Trivia gives you a real entry from the mainline games with the Pokémon's name blanked out, and you have six guesses. The text is short. Three or four sentences usually. That sounds easy. It is not, because most of the words are filler and only a couple of them actually narrow things down.
After a few weeks of playing I noticed I was reading the entries wrong. I was scanning for the most colorful word, when the useful words were almost always the boring nouns.
Habitat words narrow the pool fast
Pokédex entries almost always say where the Pokémon lives, often in the first sentence. Tall grass usually means a route-spawning Normal or Bug. Rattata, Pidgey, Bibarel. Caves and cliffs are Rock or Ground. Geodude, Aron, Onix. Deep sea is a late-game Water type. Wailord, Relicanth, Dhelmise.
The oddly specific habitats are the best clues. Old castles is almost always Yamask, Cofagrigus, or Honedge. Power plants point to Voltorb or Rotom. Volcanoes is basically Magmar, Slugma, Heatran, Turtonator.
Body shape giveaways
Pokédex writers love describing physical shape. Coils its long body is almost always a snake or eel. Ekans, Seviper, Eelektross. Shell points to a turtle or mollusc, but the kind of shell matters. Spiral shell is Omanyte or Shellder. Rocky or plated shell is Tirtouga or Carracosta.
Body part counts are unusually useful. Two heads is Doduo, Zweilous, Girafarig, or Exeggcute. Three heads is Dodrio or Hydreigon. Many tails or nine tails is the Vulpix line. Even a single horn versus two horns eliminates dozens of candidates.
Behaviour and diet
Burrows underground is Diglett, Drilbur, or Sandshrew. Sleeps for most of the day is Snorlax basically every time. Slaking, Komala otherwise. Hunts in packs is the Houndour or Mightyena or Lycanroc cluster.
Diet is sometimes diagnostic. Feeds on berries is broad but points to fruit eaters like Sudowoodo, Lickitung, Trumbeak. Drains energy or eats dreams is the Psychic-Ghost cluster. Drowzee, Hypno, Gengar. Eats tree bark is one specific mon. Heracross.
Generational tone
Each generation's Pokédex writers had their own habits. Gen 1 entries are short and weirdly violent. It can lift an elephant. Its bite kills. Gen 2 leans on folklore. Legends, omens, superstition. Gen 3 introduces a lot of weather and climate references, probably because of Hoenn's biome variety.
From Gen 5 on the entries get noticeably longer and more poetic, with a sentence or two of mood before any actual fact. If the entry reads like a nature documentary, the Pokémon is probably Unova, Alola, Galar, or Paldea. That alone rules out 500 earlier mons.
The redaction itself is a hint
We blank the Pokémon's name and obvious aliases with underscores. The length of the blank roughly tracks the length of the name. Four or five characters suggests something like Mew, Abra, Eevee, Onix, Magby. A really long blank is Stakataka, Wigglytuff, Toxapex.
Type names are not redacted. So if the entry says this Fire type, that is a free piece of information. Combine it with one habitat word and the candidate list usually drops under ten.
Read it twice before guessing
The biggest mistake I made early on was guessing on the first sentence. Pokédex entries often save the most distinctive fact for the end. It is said to be the ancestor of all Pokémon is the last line of the Mew entry, not the first.
Read the whole thing. Then re-read it. If you still are not sure, find the sentence with the most specific noun. An instrument, a profession, a number, an organ. That noun is almost always the key.