As a novice runner, the first obstacle to overcome is yourself.
While training, everyone says that running a marathon is 80 percent mental (screw that, my body begged to differ), so the biggest challenge was letting myself fail. Just as you can't start with a 250 lb. deadlift, you can't jump into training at an 8-minute mile. Sure, your competitive nature would love to train at a 1:45 hour race finish time, but if you want to make it past a week of training you have to mentally and physically slow down. There are a bunch of running schedules you can find online (like the ones from Hal Higdon, for example), but accept the fact that it's OK to modify based on your ability and schedule, and set realistic, achievable goals in terms of mileage and pace.
Take this time to find yourself as a runner. Do you prefer training indoors or outdoors? It's a lot easier to jump off a treadmill versus running outdoors where giving up means you'll still have to walk home. Are you a team player or a soloist? Find a running buddy who is just a little bit faster than you to keep you challenged, otherwise work on an awesome playlist to keep you pumped throughout your run. And find your solemate—stop by a running store to analyze your gait and find the proper sneaker (turns out the stability, cushioning shoe I splurged on would help ease shin splits my overpronating feet).
The Art of Marathon Running >>>