Can anyone give me advice for my GPA?

Right now, my GPA isn't that great considering I have about a 2.8. I would be content with going to the community college in my area and living at home for a couple of years, but for personal reasons, I really need to get out of my home environment. I'm currently a junior and am interested in attending Columbia College or DePaul in Chicago (I'm in a pretty good range for Columbia considering it's open admission but I'm iffy about DePaul). I need to get my GPA up before I start applying to college. If I were to ace the first semester of next year, would I have around a 3.0 to put me in a decently good place? How do colleges look at your senior year? When am I going to start applying to begin with?