A nature is easiest to choose after you know the Pokémon's job. Instead of memorizing a nature for every species, decide which stat the set needs most and which stat it can afford to reduce.
That approach keeps working even when the same Pokémon has several viable builds.
Choose the role before the nature
A fast physical attacker, bulky special wall, slow Trick Room attacker, and mixed attacker can all prefer different natures even when they are the same species. The role determines the stat priorities.
Write down what the Pokémon must accomplish before selecting the nature.
Physical attackers often lower Special Attack
If a set uses only physical damaging moves, Special Attack may be the easiest stat to give up. Adamant raises Attack while lowering Special Attack; Jolly raises Speed while lowering Special Attack.
The choice between them is usually a power-versus-speed question: does the set need extra damage, or does it need to move before specific opponents?
Special attackers often lower Attack
Special attackers commonly use Modest for more Special Attack or Timid for more Speed, both lowering Attack. Again, the correct choice depends on the role and speed benchmarks rather than a universal rule.
Some sets still care about physical Attack for a coverage move, so check the full moveset before treating it as a disposable stat.
Defensive natures depend on the threats you need to survive
Bulky Pokémon may boost Defense or Special Defense and lower an attacking stat they do not use. The more competitive the environment, the more likely the choice is tied to a specific damage calculation.
For general play, matching the nature to the side of defense the Pokémon is expected to use is usually a reasonable starting point.
Speed-lowering natures are sometimes intentional
Not every Pokémon wants to be fast. Trick Room teams and certain slow strategies can prefer a Speed-lowering nature, sometimes alongside a low Speed IV, so the Pokémon moves earlier under reversed speed order.
This is a good example of why “always maximize every stat” is not a complete competitive rule.
Use neutral natures when the tradeoff is not useful
Neutral natures do not change final stats. They are perfectly usable when you are not optimizing a role or when changing the nature is not worth the effort for the content you are playing.
For a dedicated build, however, a beneficial nature is usually one of the simplest ways to align the Pokémon's stats with its job.