Make a connection with your PR company to acquiesce the best results.  If the first PR agent doesn’t seem like the perfect fit, ask to try again.  Once a connection has been established however, it should be easier to get the required results.
Talk to the PR agent about your goals; discuss how realistic they are and what is needed to accomplish them.  Establish together a time-frame for reaching these goals and then work out who is needed in the firm to work on these matters.  Keep time-tracking and perhaps put someone in charge of making sure everything is on track. Regularly consult with your PR agent.
If you find after a set amount of time that the results are not forthcoming, have another discussion with your PR agent to see how to better move forward on the matter. Honesty, connectivity and goal-setting is essential for ultimate success in working with a PR firm.