USAJobs setup
Create a Login.gov account and a USAJobs profile. Upload 3–5 versions of your résumé tailored to different agencies (HHS, DOD, DOJ each look for different things).
Pathways
Recent grads or current students: apply through the Pathways Program. It's the federal equivalent of paid internships and feeds directly into permanent GS positions.
GS scale
GS-7 = entry, GS-9 = master's-level entry, GS-11–13 = professional, GS-14–15 = senior. The full pay scale (with locality) is at opm.gov.
Veteran preference
If you served, claim your veteran preference. It moves your application up significantly.