Identify champions
It can really help you to engage with a decision maker if you can identify and build a relationship with a 'champion'.
You can have either an internal or an external champion. An internal champion is someone located within the department or agency you want to influence, who will help ensure that you are heard. An external champion is someone outside the decision making body you want to engage with, but who has influence, usually because they are well known and have a particular understanding of, or interest in, the issue.