How do they film sword fights?

Answer 1

They are choreographed just like any other simulated fighting in a film, and the shots are planned. Also they may not occur in the sequence in which you see them but may be filmed more than once from different angles and then edited together. Sometimes, such as in Troy the actors move more slowly than is seen on screen, they later speed up the footage. This makes the movements seem smoother. Also, it gives the actors more time to play out what their next move must be in ther heads, so there are fewer screw-ups, and less takes.