Read all the installments of the AP that have been released so far, make notes as you do so. As Crothian says, the APs are stronger if you can foreshadow or introduce NPCs that might have a much larger role later in the AP. Also it helps you add some depth by being more familiar with how future events play out. Make liberal notes on these things as you go.
Swing by the Paizo forums and check out the AP forums: they are a great place to see the experiences of others running the AP and see what worked well and what didn't. I find the forum advise invaluable when running an AP.