Wendy, not bad for your first attempt. My first try at lightning was pretty bad. But a little experimentation and a little reading up on the web sure helped me out.
The hardest part about capturing lightning is where to point your camera and when to click the shutter and when to end the exposure. ok thats the second hardest, the first one is being able to see lightning first.
your camera settings look good,
did you use a tripod? a remote works wonders, if you don't have one for the 300d there is a Nokia or Motorola cell phone head set that can be found at the dollar store that will work with just a snip and a piece of electrical tape to cut off the ear piece.
just be patient and take lots of exposures and you will get some great shots like this one I got last week
http://www.nightshooter.com/D60/Land.../IMG_4985.html
for every good shot like the one above i posted, I have about 50 like this
http://www.nightshooter.com/D60/Land.../IMG_0991.html
I have been out a few times trying to get lightning and got absolutly nothing but a bright sky. so not every time I go out I get great shots, it just really depends on the weather.
James