A coach with mounds of experience
15 players who buy into the coach's philosophy
One star player
4 Quality starters
A pile of players who know their role
A gymful of supportive fans
A dab of luck
Start with a head coach who emphasizes all parts of the game. He must recognize when to push the players and when to back off.
Get 15 players who all buy into the coach's system. They must not question his actions on or off the court. One of these players must be a star player, who you can count on at any moment to produce. Four of these players must be starters who can contribute on their own, but can also let the star take over. The remaining 10 must be players who all know their role, and execute it when they need to.
Next is a gym full of supportive fans. They must always support the team no matter who good or bad they play.
Finally is a dab of luck. Injuries, poor shooting, or unlucky bounces can lead to losses, derailing what would have been a championship season.
Put all these together, and you will get a basketball team that will win a championship in their respective league.