So many people nowadays use iTunes for playing music in the background while they work, check their email, surf the web etc.  However, most people only have one screen and the iTunes window can take up a large part of that!  A little tip that I find very useful is to use the "Maximise" button on the iTunes Window.  This button, which can be found on virtually any window in Mac OS, is a toggle.  In other words, the first time you press it the Window gets maximised and the next time you press it the window goes back to its original size.

The Maximize button is the round green button to be found at the top left of almost any Mac OS window.  The thing is, in iTunes, it has a special function.  Instead of maximising the window, what it does is it gives you the iTunes Mini-Player window.  It looks like this:

iTunes Mini Player

The iTunes window becomes a tiny controls-based window giving you instant access to only the controls that you really need, including the currently playing track, volume controls and the standard play/pause, forward and back buttons.  Now you can position this window wherever you like, have easy access to it without taking up your whole screen or having to switch to iTunes every time you want to pause, change the volume etc.  To get back to the standard iTunes window, all you have to do is press the Maximise button again and you're back to normal!