To me, this came easily. However there are some songs that are more difficult. The most difficult song to both sing and play is AC/DC TNT. Funny thing is it's easy to play and to sing, just not at the same time. Try to break the song up into little phrases, and work to coordinate these. Then move on to the next phrase. Soon you'll have the whole song. Make sure you have the lyrics memorized stone cold. To do this i recommend hand writing the lyrics twice a day. Don't look at the lyrics until you are truly stumped.