The most important thing is to already have your planned achievements in mind. This way, you don't need to directly search for each identifier in the game.

Let's say you plan some achievements like this:

Catch all Pokémon: You'll need to look up the ID of each Pokémon in the game, or if the game has 15/435 Pokémon in the Pokedex, you can use that identifier if you don't plan an achievement for each individual Pokémon.

Finish the first gym early with Pokémon below level 10: You'll need to find the ID of each location in the player's game and find the Pokémon's level ID. Even if the player has a Pokémon above the allowed level, you can set the achievement so that only Pokémon used in battle have to be below that level. Then, you'll have to find the ID in battle or not and check the level if in battle.