How do I rename song s on my iPhone 4 ?

You can't

Can't do it on the phone. Change the name in iTunes and resync.

You can't rename songs directly on your iPhone, but you can rename them on iTunes on your computer. The easiet way to rename on your computer is to first open iTunes, then using the right click on the song simply type in what you want to rename. Then click to where your iPhone is showed (have to have iPhone plugged in) and click sync. After the sync your song should be renamed on your iPhone. Hope this helps! 🙂