I'm pretty familiar with several of the Adobe Creative Suite programs, but I could never quite figure out Flash Professional, at least in the few times I opened it and tried to play around with it. On the one hand, it seems like a content design and animation program; on the other hand, it seems like it's a visual programming interface. Because of that, the timeline doesn't quite work the way you'd expect if you come to it from programs like Premiere Pro or After Effects. If you want to animate something, for example, you have to create what's called a "motion tween" and each animated object has to have it's own unique "motion tween" layer. Plus, layers work a bit differently than in other Creative Suite Programs like Illustrator or Photoshop.
I knew I was in over my head, and did what I always do when I can't figure out a program: pick up a guide. I think it's helpful to have a broad overview before really trying things on my own, because then even if I don't remember everything from the overview I'll remember what's possible and know where to look when I'm stuck. I've tried other kinds of guides, and found them to be useful for lots of things, but one of the best places I've found to get started with any of the Adobe Creative Suite programs is with the introductory guides they publish, the Classroom in a Book series. The Flash Professional CS5 guide didn't disappoint. This is a highly readable, hands-on guide to the wide range of what's possible with the latest version of Flash Professional. I'm still just getting started, but as a result of working through this book, I think I finally "get" Flash: what you can do with it and how it works.
They get you started doing a very simple animation to get used to the interface, then show you how to create original content, and illustrate the very important notion of symbols and symbol instances, then show the different kinds of animation you can achieve with Flash. Up through chapter 5 what they cover is how to do in Flash what you could do in other programs; it's not quite the same, but the concepts are similar and so I found I could fly through those chapters. It wasn't until chapter 6, the chapter on creating interactive navigation, that I finally felt I "got" Flash, and could finally understand why it's set up the way it is and why the timeline doesn't work the way it does in other similar programs. In a nutshell, the basic idea is that the timeline includes all of the content of an interactive Flash movie, and the programmer/designer can specify which parts of the movie to playback and how to play them based on user interactions. So a simple animation or movie is just a special case of what's possible with Flash.
I would suggest that for anyone who is coming to Flash from other programs that use a timeline, you would do best to start out with chapter 1 and then skip to chapter 6, to get a better idea of how Flash works to integrate animation and interaction, before going back to see how to create and animate content. In fact, I think it might have been better to organize the chapters that way, since once I "got it" in chapter 6 everything else was much more clear to me. Until then, with chapters 2-5 I found myself wondering why it wouldn't make more sense to just do the content creation and basic animation in other programs like Illustrator and After Effects. Now I understand why Flash is set up the way it is, and how it can work as an excellent stand-alone tool for creating designs, animation, and interactions. Subsequent chapters give more advanced tools for working with text (including dynamic text that can be embedded in a text file and varied while the flash look stays the same), and sound and video in Flash. They also show how you can program a Flash file to call up external content and how to publish the finished product for use on the web or as a self-contained program for use on a desktop.
Like the other books in the Classroom in a Book series that I've worked through (Premiere Pro CS5 CIB, After Effects CS5 CIB, and Illustrator CS5 CIB), this one is clearly written and straightforward. The instructions are precise and the clarifications are direct and to the point. Each lesson tells you what you're going to learn, it has you creating content that gives you a hands-on feel for the concepts that are being explained, and then if offers a series of review questions regarding the most important concepts. They aren't trying to cover everything or to give you all the little tricks for using Flash; but they aim to lead you from the stage of being a complete novice to having a pretty good idea of what can be done with the program. It was exactly what I needed to get started. After that, you are prepared to experiment, but also to see the value of more advanced guides that show different ways to do some sophisticated things with Flash.