1. Keep him alive - A classic rule. Before the big explosion, the villain must be on the brink of death. Shot, Beaten, bloody, but still alive.....barely. Keep the bad guy alive just long enough for that timer to hit zero.....otherwise what's the point?
2. Show it - When the climactic explosion goes off and the villain dies, I don't just want to see the explosion in the background as the hero runs away. No, I want to see the bad guy being engulfed by flames or exploding into pieces, no off-screen cheapness.
3. Outrun the fireball - Laws of physics? Pffft... not in this house. Another classic rule where the Hero must outrun the final explosion in a fashionable and death-defying way. The explosion must be the biggest of the film, flaming projectiles are optional.
All these rules are covered above and beyond in The Long Kiss Goodnight. The scene involves a truck bomb that is supposed to blow up the bridge at Niagara Falls. As Charly(Geena Davis) is attacked by the bad guy from a helicopter, she uses a dead body as a counterweight to lift herself into the sky and shoot him. He falls and lands on top of the truck bomb.....and the fun begins.