You can do this by editing the disc information whenever you rip a CD using iTunes. However, if you want to clear everything, it is pretty easy to do. Highlight every song in your iTunes library, right-click on one of them, left-click on Get Info, put a checkmark next to "Artist" making sure it is blank (you should NOT do this as that will only mess your iTunes library up) and do the same for "Year." However, like I said, deleting the Artist field for everything will mess your iTunes library up pretty bad as iTunes tends to require basic information such as artist, album title, genre, and track number in order to properly display content. If anything, you will be fine with making sure the Album Artist field is left blank rather than the actual Artist field.