I'm trying to cut down my 1.5 mile run time. What do you all do to train to improve your run time?

I'n not the best runner in the world and I'm looking for tips to better my running.  I do pretty well in the push-ups and sit-ups, but barely pass the run.  Any tips would be much appreciated.  My goal is to max all my numbers eventually.  I know the first reaction is "run more" but that only helps so much.