In these fields and others, the chance to make contacts is an important advantage of graduate school. I've gotten plenty of calls from people at the master's level who have never done internships, and there is just no place to go. They wind up as bank tellers. Certificate programs are increasingly popular in certain fields, including technical writing, computer graphics, and local area networking. Such programs last anywhere from 10 weeks to 18 months and are beginning to lure students away from more conventional graduate programs.
Career counselors give the certificate courses mixed reviews.
If you are a dislocated worker or someone whose skill set doesn't match what employers are looking for right now, they may be just what you need to get back on your feet. Though they may help you get a job quickly, you could find yourself stagnating before you know it. Roni Noland has high regard for some certificate programs, particularly those in human resources and paralegal training. If there is, I would go for the master's. In the end, there is probably no simple guide to determine whether graduate school is for you.