Create pet projects for yourself , preferably ones that contain a facet of Flex/AS3 that you haven't used before. This will expand your proficiency with the language when there is no pressing cause. For example , my pet project is going to use video when completed , but others may involve things like remote services , modules and so forth.
Learn a framework , dependency injection based , so you can develop faster. Without reinventing the wheel.
STUDY application architecture , bad architecture can sink an application/project and good architecture helps solve problems before they rear their ugly head. I've seen bad architecture destroy projects , and contrary to popular belief , these deficiencies don't resolve themselves over time or disappear.
Google is your friend.
Learning how to spell, is also important.