When utilizing a professional social media site liked LinkedIn, I like to approach them with the mission of creating an online persona, that most businesses that operate in my employment area. My persona is a jack-of-all-trades that can fix problems. Its hard to create a persona online so let the groups and the people you link with help.
I personally follow groups that are associated with the military and the rate in which I was a part of when I was a service member. In the government job arena, knowing that jobs are available and who is doing the hiring is important and LinkedIn can assist you in finding those jobs.
Groups I follow in LinkedIn: