Go to the on-line version of Runner's World and check the training site on the left of the screen. That's only a mile further than last week, but subtle mileage changes work best. Run this at a comfortable pace 45 to 90 seconds slower than your race pace. If you're feeling frisky, pick up the pace a bit in the last 2 miles, but don't feel you have to finish in a sprint because I gave the green light. And be cautious about dueling with training partners, since excessive hard running is counterproductive.
Consistency is what counts.
Improvement comes easily when you begin from a base of zero fitness. After that, you need to learn how to train properly.