Quick answer if you use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its subfolders and files) intact to the other drive. Open iTunes and immediately hold down the option (alt) key (shift on Windows) so you get a prompt to select a library, then guide it to the 'iTunes Library.itl' file in the moved iTunes folder.
If you put the copied iTunes folder in the default location of Macintosh HD > Users > *User Name* > Music then you don't even need to start with the option key held down, iTunes will automatically look for it there. (Make sure there isn't anything already in the iTunes folder there that you want to keep since you will be replacing it with the one you are moving.)
Longer answers if for any reason you do not think all library files are inside your iTunes folder (changed preferences settings at some point):
iTunes: How to move [or copy] your music [library] to a new computer [or another drive] - http://support.apple.com/kb/HT4527 - a somewhat bewildering and not always easily understandable set of options.
For the record there's this reference for iTunes 11 but it really doesn't strike me as having the specifics you need. iTunes 11 for Mac: Move your library to another computer - http://support.apple.com/kb/PH12168
2011 ilounge article: Transferring your iTunes library - http://www.ilounge.com/index.php/articles/comments/moving-your-itunes-library-to -a-new-hard-drive/ - An article with good background information (similar to the links above), particularly if you are not sure your media files are all grouped for quick answer above. Unfortunately under the single term "transferring library" it describes two very different moves; relocating just your media (not really transferring your library and not recommended unless you really need this configuration), and relocating media+database (really your whole "library"). Make sure you understand the difference before electing to move only media.
Windows users see tip at: https://discussions.apple.com/thread/4095896?answerId=18879381022#18879381022
Consider moving everything from a Windows PC to your Mac in a single move, including your iTunes library: About Windows Migration Assistant - http://support.apple.com/kb/ht4796 - Learn about how to use Windows Migration Assistant to migrate your files from a Windows PC to a Mac.
