Then on the flash tab you can adjust the quality of your bitmaps and mp3s used in the movie. Also try using vectored graphics instead of bitmaps. And try not to use as many effects such as gradients etc
File, Publish Settings, (then make sure your on the Flash tab) and under the section called advanced there should be a check box that says "Generate size report". After you check it just press the publish button at the bottom and your done.