What Team Preview is and how to use it
Before any VGC doubles battle starts, both players see the opponent's full 6-Pokémon team and choose which 4 to bring and in what order. That phase is called Team Preview, and playing it well matters as much as building the team.
Why only 4 of 6?
Standard VGC uses 6-Pokémon teams but only battles with 4. That turns every match into a small deckbuilding decision: you don't always bring your 4 "favorite" Pokémon, but the 4 that best answer the specific team in front of you.
Seeing the opponent's full team before deciding is the single biggest information advantage in the format — skipping that read gives away the match before turn 1 even starts.
How to decide what stays home
Ask yourself: which 2 of my Pokémon have the worst matchup against this specific opponent? Those are usually the ones you leave out — not the "weakest" Pokémon in the abstract.
Pay attention to who can set Trick Room or Tailwind on the opposing team — if your team relies on its own speed control, your bring-4 order (who leads) changes depending on whether you expect the opponent to flip it.
Common mistakes
Always bringing the same 4 without looking at the opponent. Team Preview exists specifically so you don't do this.
Ignoring lead order: in doubles, who leads on turn 1 determines what plays are possible (Fake Out, Follow Me, Intimidate) before the opponent even moves.