Just because you may not want to go to college doesn't mean that you shouldn't think about your future. Keep your options open to these and other career paths. Even if you're considering the non-collegiate route, keep on taking the college prep curriculum. You never know when you might change your mind. This is great practice for the ACT and SAT tests that you will need to take next year.
Some colleges even offer scholarships to students with excellent PSAT scores.
Also, registering for and taking this test will get you on the mailing lists of lots of colleges and universities, so you can find out more about what's out there. Some high schools offer classes on how to boost your ACT and SAT scores. You can also buy study guides and practice tests that can help you learn the tricks of taking these tests. There is a wide variety of materials and classes designed specifically for ACT and SAT test preparation that can help improve your scores. ACT and SAT both have practice booklets, as well.