this is how i fish it:
the first is to cast it out, reel it down, then start twitching/jerking it around. then leave a long pause, then do it again...and occasionally reel it straight for a few feet.
another is to cast it, jerk it hard, and keep doing this. this will get the most erratic action out of it, and is probably the most popular way to fish it.
the last method is to just reel it straight back like a crankbait. this usually isnt very productive.
here are some rapala links on how to fish it:
http://www.rapala.com/products/howto/fish/index.cfm?lurename=x-rap&freshorsalt=Fresh
http://www.rapala.com/pdfs/instructions/x-rap.pdf