Location, Location, Location
Where a boss fight takes place is just as important as the design of the fight itself. The level is an extension of the boss fight … and sometimes, the level IS the boss fight.
The basic boss fight takes place either in a circular arena or a linear screen-wide walkway. This allows the camera to stay focused on the boss, who generally inhabits the center or back of the room with occasional trips to the side and outer edges. For more dynamic boss fights, add elevation to the arena. Devil May Cry had an interesting fight in which the player kept alternating between fighting the boss high up on the walls of a castle and down low in the castle’s courtyard.
Think about the boss in relationship to the environment. How will a boss use the level for movement or attacks? Having dynamic elements like collapsing statues or walls or break-away floors can keep things exciting and surprising as the environment gets wrecked by the boss (and the player) over...