Three important recommendations include:
1) Work to develop real relationships by meeting in person whenever possible rather than relying entirely on email.
2) Call out the situations and individuals that help you succeed to help bring visibility and foster competition.
3) Secure trust by communicating clear expectations of what you will deliver. Then deliver. And if you fall short, own up to it.
A more complete list of recommendations for securing support for sales and sales management can be found within the Customer Reference Handbook. Even if your program is heavily focused on just producing marketing deliverables, the sales team is both your supplier and end consumer. It is essential to make sure that they are engaged in the process.