How do you clean up ipod names/artists/covers? READ MORE?

How do you get the name of the song and who sings it to come up instead of unknown and track 1 etc. I have an albulm unknown on my ipod and track1 5 times then track2 5 times etc. all diff. songs but i want to know what they are instead of under unknown/track and there already on my ipod so wud I have to clean it then import them again to my ipod ? and wats a GOOD and maybe free cleaner ? THANK YOUU