Co-writing: The art of sharing your heart felt ideas with another person and trusting the 2 of you will create songwriting magic. This can be tremendously rewarding and often frustrating. But there are some guidelines to make this experience often a great one. If Moses came down from the mountain with a tablet or two on co-writing perhaps this would be chiseled in the stone!
You shalt put nothing else before the song. The Song Is King. Leave your ego at the door. Let the song develop as it wants to develop and not as you are determined to force it.