How do I transfer my iTunes library from one computer to another?

How do I transfer music I didn't buy on my iTunes library to another one, on another computer?

• I didn't buy any of these songs, and they're on my iTunes library, so I wanna transfer those songs to another computer, that has an empty library. Not just the files, everything I edited on iTunes too! I have an iPod that contains all these songs.

• Answer:

  In fact, once you've put the songs or video on iPod or iPhone, you can get them out of iPod or iPhone and put them on computer. If the songs are purchased from iTunes. you can easily transfer them to iTunes or computer by clicking "Transfer purchase". If your stuff are downloaded from other website. you can transfer them to computer with iPod transfer. like this one: http://my-media-tools.posterous.com/ipadiphoneipod-transfer-tools