Can’t let go of his / her own ideas. If you can’t ever accept that someone can have a better idea than you do, you need to write alone. I have written with people who never liked any ideas I had and I got the distinct impression that my role for the day was to tell them how great they were. That is not a co-write session. That’s a praise session. And those writers don’t need me or any other actual writer. They just need someone to praise them, and that someone literally can be anyone. Good co-writers listen well, and they can let go of an idea if a better one comes along. A great line can kill a song if it doesn’t work in context. Let go of any sacred cows and let the song to be the king. Do whatever is best to serve the song in every instance.
Doesn’t contribute. I have cuts with co-writers who only contributed one line to the song, but they tried hard and participated all day long. That’s fine. What’s not cool is a co-writer who is on the phone or the Internet all day and is never really engaged in the process. Basically, the type of co-writer who is sitting there and exists in the room physically but it’s just physically! This happens more than you would imagine. Stay engaged and throw out ideas. Even if they are bad, they may spark the right idea from someone else. At least you are “trying” to contribute. If it works or not is another matter but trying to contribute is the minimum you can do.
He / She is in awe of your success. Co-writes where one person is in awe of the other turn into fan club sessions. Nothing really gets done because one person is afraid to challenge the other. You are not going to tell someone you are in awe of that their line is no good or their melody is boring. Tell yourself that you deserve to be in the room and that you have something too contribute. If you can’t make yourself believe that, you are probably not ready for this co-write yet.
Continually calls or emails to ask about the song after you finish the co-write. It’s hard to be a new writer and not get any feedback from your song, but you don’t want to ruin your writing relationship with a great co-writer by bugging them to death about the song. If the song gets put on hold or gets cut, they definitely will tell you. If not, there is nothing to tell you. Trust that your co-writer will let you know if something happens with your song. Until then, take a deep breathe, and work on the next song. Collaboration with another writer is a relationship you want to treat with respect. Be sure the song belongs to your co-writer as much as it belongs to you, and they will try to get the song to go somewhere as much as you would. Keep asking has no result other than irritating your co-writer and making them not want to write with you anymore!