Hello, to accurately give you information, we must know more about your current fitness and training. What mileage were you running when you ran your personal best of 1:32 half, and what type of mileage? (i.e., any long runs, any marathon pace runs, any tempos, any 5k/10k pace workouts, etc)
As someone said, you will have to be able to run faster at the half. In general, when one wants to get faster at the marathon, if the body can take it, more mileage is the way to go. Ideal training for marathons should include marathon pace runs, lactate threshold runs, and some plans include speed workouts. A weekly long run is important as well.
Some background on myself - I am actually training for my 3rd marathon right now, with a goal of 3:05. My 2nd marathon was in February, and I was right on track for sub-3:00 after 24 miles but took a wrong turn and ended up with a 3:14. Then I took a lot of time off running and am getting back into it. I'm running 70-90 miles per week for my training, and for my last one, I ran 80-100 miles per week. I am following a plan in a book by Pete Pfitzinger and Scott Douglass - called "Advanced Marathoning". I recommend it if you're interested - has all sorts of information about marathon training - nutrition, physiology, cross-training/flexibility/core workouts, and training plans, ranging in mileage from up to 55 miles, to 85+ miles.