RPG Mechanics IV : Boss Balancing and Strategy

Bosses are a culmination of what you've learned so far as a player. The monsters you're eased into during the level prepare you for your encounter with their overlord. Self-contained bosses with strategies unique to themselves, offering your battle with them as the only lesson, are best left for optional content.

A strong, recent example of this philosophy is Twilight Princess:

1) Kill stuff with your sword.
2) Kill stuff with bombs.
3) Find a Boomerang.
4) Solve puzzles by grabbing bombs with your Boomerang.
5) Solve puzzles by hitting several targets in one throw with your Boomerang.
6) Dodge for dear life, grab and redirect bombs at the boss with your Boomerang, and then obliterate him with your sword.