@joannekwan gave some excellent advice. I agree entirely.
Communication is supremely important between any people collaborating. You may also wish to draw out some simple contracts. There are some places online that will give you tips on how to do that.
But on contracts: don't be unwilling to amend your contracts. Likewise, never sign a contract that you aren't comfortable with. Let them know that you need some things negotiated or adjusted, and if they're unwilling...walk away. Contracts are about compromise, and you should never give someone legal justification for abusing you.
On relating to art as a writer: don't micro-manage the artist or the art. Don't be tempted to micro-manage; let them do their job and create and direct the visuals. It will almost always lead to a better final work.
But above all, I feel like it's a great idea to concentrate on open, honest, good communication between everyone participating in the project. So many problems could be avoided, in my experience, by people communicating clearly between themselves and being honest, and not drawing things out for lack of communication. It is usually much better to discuss a problem when it presents itself, and after leaving something unaddressed for a long time, it can make it so much harder to deal with.