Some questions that need to be answered before you can get any sure advice are, when did you take the LSAT (all 3 times)? What's your UGPA, and how long ago did you graduate?
Also, what makes you convinced that you will do better this time around? Have you taken any diagnostic tests? If so, what were the scores? Did you take any diagnostic tests before the first 3 times... and how were the scores?
Also, what schools did you apply to and when? Were you waitlisted anywhere?
I would recommend taking a prep course, they're kind of expensive but the amount you increase on the LSAT (which translates to money from the University) is worth it! But, one very, very important thing with the prep course. When you go you have to do ALL the work! Too many people skip classes, don't do the homework, and don't ask questions when confused. These things are necessary for getting a big score increase, because a prep class can help you tremendously... but they can't do the work for you. I would suggest taking a prep class (I don't know when they start in your area or how long they run for), then taking the February or June LSAT... then applying in a year for the Fall 2010 cycle (granted, only if you have atleast a 20 point increase on your LSAT). The reason behind this is, people who are huge splitters (I am one as well, but the opposite splitter from you) are always risky for law schools to take and it can really go either way. The number one way to increase your chance to get into law school being a splitter (or really anybody) is by applying very early in the cycle (basically apply EA to all schools you can that are non binding, and apply to all schools by Nov. 1). By taking the December LSAT, then having to wait for the scores to come out, is just not a wise thing to do in the least. It's too late in the cycle. Why are you not considering the October LSAT... that will be early enough for you to get your applications in EA and by Nov. 1. Is it because the time period between LSAT's is still in effect during October?