Step 1: Establish a Relationship with Your Producer

By establishing a positive relationship with a producer, you are taking the first important step toward a successful relationship with a game publisher. Prior to having a deal with a publisher, a producer can:

Recommend you for a project he has. When a producer has an upcoming project, he will be on the lookout for a good development team. He will typically have two to three developers in mind whom he will contact to get proposals.
Recommend you to other producers within his company. The producer will know which projects are getting funded and are in need of a developer. If you are on good terms with him, he might recommend you to other producers.
Help you prepare for a successful pitch to the publisher. The producer can provide you with document templates and sample information to help you prepare the most effective pitch possible.
Help you with key introductions within his company. By introducing you to key decision makers within his organization, he can help you extend your network throughout that company. Those relationships might even outlive the producer's employment with that publisher.
Alert you to opportunities for contracts or product proposals. The proper timing can significantly increase your odds of obtaining a contract with a publisher. Knowing when a publisher is looking for developers and what types of titles they are looking to publish will help you focus your presentation or pitch.

Once you have inked a deal with a publisher, the producer assigned to you can help you with the following:

Put together the perfect project plan. Most publishers have approved examples of technical designs, game designs, schedules, and budgets. Having these available prior to starting your work on these deliverables will help ensure a quick approval and a happy publisher. If a producer does not offer these documents, ask for them.
Proactively keep you on good terms with the publisher. If you succeed, he succeeds. He will review your progress, alerting you to any potential issues in terms of milestone approvals, direction, or impending changes with the publisher.
Get you a quick sign-off and prompt payment for your milestones. Assuming you meet your milestone, most producers can expedite approvals and check deliveries. Remember however, that getting you an expedited payment is extra work for a producer.
Gain support for your product from other divisions. A good producer knows how to get the most from the various other organizations within his company. This can translate to increased marketing, public relations, and sales support.
Recommend you for future work. Do a good job and maintain a positive working relationship, and he will recommend you for additional work.

Unfortunately, not developing a positive working relationship with a producer will affect both your short- and long-term business goals. A negative relationship with a producer might:

Make it difficult or impossible for you to ever work for that publisher or even perhaps other publishers as long as he is employed there. This situation can cost you additional work with that publisher and any future publisher for whom he might work.
Critique every milestone approval to the point that it is impossible for you to successfully complete your project. A producer can make a developer's life miserable if he so chooses. Having very well-defined milestones and a solid, approved project plan can help prevent this.
Get your project canceled. A disenchanted producer can get your contract cancelled in the hope that a different developer can do a better job.
Speak poorly of your company to his peers. The producer network is very tight. Most producers have worked for several publishers and have a solid network of peers. Obviously, it is important to always maintain a positive relationship with your producer. This is especially important when things go wrong, as the producer can help you stay in good graces with the publisher. This might enable you to work with that company again in the future.