There are a lot of ways you can control iTunes from the keyboard, letting you search for songs, play songs, and even create playlists. Here are some useful tips.
The spacebar, which works as a play/pause button, is probably the most commonly used iTunes keyboard shortcut. It works both when iTunes is in its full-size window and when it's in the mini-player window (click on the green button at the top-left of the window to toggle between the two). Pressing the right or left arrow key in view mode allows you to quickly skip ahead or back, respectively, between tracks; it's just like pressing the next or previous button on an iPod (in other modes, command-arrow is needed). You can also skip ahead or back within a track that's playing by pressing command and option with the right or left arrow keys; this jumps the song by five-second intervals. If you're browsing media, you can also start playing a selected item by pressing the return key. (These shortcuts work with all types of content: music, videos, podcasts and audiobooks.) You can control the volume using command-up-arrow and command-down-arrow to raise and lower it, respectively; command-option-down-arrow mutes iTunes, and command-option-up-arrow restores the volume.
When you're playing video, you have a number of additional options. To change the size of the video, press command-0 (half size), command-1 (actual size), command-2 (double size) or command-3 (fit the screen). You can also view full-screen video by pressing command-F, and you can get out of full screen by pressing the escape key.
While you may know these basic shortcuts, there are also some browsing shortcuts that let you find and choose music without resorting to the mouse. For starters, if you want to search for something in your music library, click on that media type to select it, then press command-option-F to make the search box active. Type in any text you want--a song, artist or album name--and iTunes will narrow down your music to just those tracks that contain your search term. You can do the same with any of your media types: music, movies, TV shows, podcasts, or audiobooks. You can't, however, perform a global search among all your media types, unless the global library is visible. (Doug Adams' Change Hidden iTunes Preferences application can turn on the global library so you can search all of your content at once.) Once you've found what you want to listen to, you can use the tab key and arrow keys to move around in iTunes and choose what to play. From the search box, press tab once to move to your library (if the iTunes Browser isn't visible; more on that later), then use the up- and down-arrow keys to navigate. You can keep tabbing around to move through all of your iTunes content. The tab key will cycle from your music library, to the search box, to the list section of the iTunes window. When you get back to your music library, in the source column, just press the down-arrow key to move to other content: to other libraries, such as movies or podcasts; to playlists; and to folders, but only to their contents when they are expanded.
There are some exceptions, however; Apple makes things slightly more complicated when you use different views. For example, in Cover Flow view, pressing the left- or right-arrow key takes you to another album, not another song, even if you're playing something. When you're in grid view, the arrow keys move you around the grid, and return takes you to the contents of an album--displaying a list of its tracks--from which you can use the up- and down-arrow keys to choose a track to start playing.
Earlier, I mentioned the Browser; that's the two-column (or three-column, if you're using Change Hidden iTunes Preferences) Browser that displays at the top of the iTunes window when you press command-B. You can use the tab key to move from column to column: if you're in your music library, tab takes you to the search box, then to each of the Browser columns, then to the iTunes list pane, then back to the music library.
There are plenty of other keyboard shortcuts that you can use when working with iTunes: just choose Help: Keyboard Shortcuts to see a list of them.
[Senior contributor Kirk McElhearn writes about more than just Macs on his blog Kirkville.]