Avoid the temptation to "store" unused objects offstage in the work area; they'll still be export-ed in the final movie and will add to the file size, prolonging download times.
Clicking the small triangle-shaped icon in the bottom-right corner of the Property Inspector toggles visibility of the bottom half of the panel, which contains controls that are considered secondary. Hiding these controls is not recommended for the novice so that you don't wasted time hunting around the application when you do need them.
The Library panel in Flash differs from other panels because you can have multiple instances of it open at the same timeone for each Flash document you have open. While handy, it can also be confusing when you want to access a symbol but are looking at another document's library. For easy identification, the name of the file is appended to the panel title.
Need a custom user interface element that's not included in Flash installed components? Many custom components can be found on the Macromedia Exchange for you to download and install. The Exchange is located at: http://www.macromedia.com/exchange