I applied online. I interviewed at US Department of Justice (Sacramento, CA) in Oct 2015
Interview
Department manager and most senior tech had the interview. Asked me a few standard questions, but were mainly concerned about the personality fit and teachability of the prospective employee.
Apply through USAJobs. Wait to be referred. Once referred, HR will contact you to setup an interview. Once you have the interview, you will meet the supervisor and other co-workers.