Why isn't my iTunes syncing to my iPhone?

I've put new music on my iTunes library and i want it on my iPhone, but it won't work. It will say that it will back up my phone and then that it has put my music on there, but it won't actually put it on there.

Try repairing your itunes through add or remove progams

If you are not manually managing you music in iTunes (but instead have checked Sync Music on the Music tab of your iTunes sync settings), check the following:

On the summary tab of your iTunes sync settings you have checked "Sync only checked songs and videos"
In your music library you have checked all the songs you want to sync to your phone
There are no exclamation points next to any of the songs you want to sync to your phone
You have authorized your computer for all Apple IDs for purchased music you want to sync to your phone (in iTunes>Store>Authorize This Computer)
You have checked "Sync Music" on the Music tab of your iTunes sync settings

Are all these correct?