iTunes

iTunes is sooo confusing!
If anyone has an iPod and uses LimeWire and iTunes, PLEASE READ.

Ok so I download all my songs from LimeWire. I don't know how you guys got your songs over from LimeWire to iTunes so the songs went onto your iPod, but I made a play list called 'iPod Music'?? It worked but now that I have downloaded more songs, some of them transfer over to my iPod when others don't! Its soo annoying I don't know what to do. There are 3 folders with music on them IN iTunes. 'Library', 'My LimeWire Tunes', and my play list that I called 'iPod Music.' Now the annoying part is that each folder has a different amount of music on them. The only one that has all the songs I want it to have on my iPod is of course 'My LimeWire Tunes'. I don't know how to make the 'Library' and my iPod have the same amount of songs on it as 'My LimeWire Tunes'. Should I delete my 'iPod Music' play list and create a new one? Is there an easier way?
PLEASE HELP! Thanks in advance.