Pick a format first
Choose a clear win condition
Build around one main strategy
Include strong type coverage
Add reliable defensive pivots
Add speed control
Include hazard control
Include hazard setters or removal
Check for common threats in the format
Balance offense and defense
Avoid too many shared weaknesses
Make sure the team has a plan for bulky walls
Make sure the team has a plan for fast attackers
Make sure the team has a plan for setup sweepers
Use Pokémon with good synergy
Cover status and utility needs
Test the team on ladder
Adjust based on repeated losses
Keep the team consistent
Use legal and optimized sets for the format