I am going on an interview for a purchasing agent position. Does anyone have any advise?

I have a year of experience with a company that provides services to governmental institution but I am looking to get on the other side of the procurement process. Does any work as a civian purchasing agent for one of the branchs of military? If so can you help me find information that might help me land this job. I really need to change jobs, the company I work for is sinking like the Titantic.