How do you import songs from your ipod into the itunes library without all the songs getting deleted?

I wanted to know if there is anyway you can put songs into the itunes library without all the songs on the ipod itself getting deleted. I was told you can do that but i dont know how.How do you import songs from your ipod into the itunes library without all the songs getting deleted?
RIGHT CLICK YOUR IPOD ON I TUNES IPOD OPTIONS and find manually manage music or on itunes 7 left click your ipod there is a section called optins click manually manage music and your done