Regarding Federal jobs:
1. Usual "one page resume" rules don't apply. Because the government is supposed to be accountable and stuff, they want a complete, objective account of your qualifications, not an elevator pitch, so your resume can (and should) be more like a Curriculum Vitae than for most jobs. Follow all instructions exactly to avoid being disqualified.
2. The hiring process tends to be a lot slower, so you may end up spending less time actually working. For example: you might apply over the winter, but due to the length of the application process, background checks, etc., you might not start until June while all of your friends are starting their internships in May and April after classes are over. Maybe it's gotten better, though; my agency seems to be able to hire more quickly than in the past. And they do seem to be pretty flexible with scheduling work over breaks or on days you don't have class during the school year, so there's that.
Networking is probably a good idea. Get your face in front of people. Make them remember you. Make yourself a real person to them, not a piece of paper with words on it.