Article: Once you have manual management, you can set up autofill to quickly sync specific content areas when you plug your iPod in. It is located at the bottom of the main iTunes window. You can also choose to sync a single playlist. Click on the "Autofill" button on the far right. iTunes will then automatically sync as much music as possible from the content selection you made to your iPod. If your iPod cannot hold all of the content you selected, iTunes will simply stop syncing when it is full.

What is a summary?
Set up manual content management using the steps above. Click on your music library and look for the Autofill settings bar. To sync music, choose "Music" from the drop-down menu next to "Autofill" to sync your entire music library.