Here are some tips:
If all your songs were purchased from iTunes store, use "Transfer Purchases" option to transfer. See http://support.apple.com/kb/HT1329
If some of your songs were from other sources, you will need to utilize some iPod
transfer program to help you, like this handy one called Tansee iPod Transfer
Many of my friends are using it for its easy and safe transfer.
With just a few simple clicks, it will help you transfer all songs/videos from iPod to your selected folder on your computer, and then you can also easily add those files back to iTunes.
More importantly, this won't overwrite any original files on your iPod. And all song names are preserved.
Here is the step-by-step guide on the whole process:
You can also search more other ways at http://ask.com