Glance at the After Effects Help Site from Adobe. This reseource is always available if you need help.
View the video overview of After Effects CS5 (CS4 has almost all of the same capabilities and features). When you are finished, write in posterous one or two effects that you did not know about that you were interested in. Also share specifically how you can possibly use it to animate your project (e.g. lens flare when the sun sets over the mountains in my story).