If you are interested in getting a government job, the main thing to remember is to investigate as many job listings as possible to be certain that you find a career and a department or agency that's a good fit for your talents and your personality.
The first thing to do when you're searching for a government job is to check government web pages for openings. Make sure you only send a resume and cover letter if you have the skills and training required. Most government jobs aren't the kinds of positions that offer on-the-job training, so you'll just be wasting your time applying for jobs for which you aren't qualified. The bright side here is that there are always plenty of openings with the government, so you should have plenty of options to sort through. On the other hand, don't be afraid to apply for a particular government job if you are overqualified for it. Once you get that job, you may find that you will have a fairly easy time switching to another, higher-paying job for which you are more suited.
If you are still in school, there are certain sectors of the government that will probably be offering more jobs than others in the future. Among these job-rich fields is health care, which will need many more employees given the recent expansion of health care. And if Congress ever creates a public option for health care in the future, which is possible, or a single-payer system, which is less likely, then look for the number of health care-related government jobs to skyrocket. Education is another job-rich segment of the government; as our population keeps expanding so do the number of schools, and thus the number of administrators needed to keep tabs on them. The government might also soon invest heavily in environmentally-friendly, or "green" jobs, including renewable energy technologies. Our nation's roads and bridges are crumbling, too, and therefore government engineers will soon be in higher demand. (Federal contracts for private engineering forms and construction will also become widely available to help take care of these jobs as well.)
Be prepared when you are applying for a government job to fill out many complicated forms, and make sure that you follow directions exactly on every form you fill out. Don't rush through this paperwork; allot yourself plenty of time to read the directions and understand what information is being requested. Most government job applications also require KSA statements. These are mini-essays in which you explain why your knowledge, skills, and abilities (those are the K, S and A) fit the position for which you're applying. Make sure you have a through KSA list handy whenever you fill out a government job form. Finally, it can take quite a while to hear back from the government after you apply for a job, so be patient and try not to get discouraged.