Run. A lot. - It may sound obvious, but more running, and the more your body gets used to running all the time, the more it will be used to it when you really need it, like on race day.
Have a purpose for your runs - Why are you running today? Is it a tempo run for speed, a long run to train for the distance? Fartlek? Just to clear your head? Walk out the door knowing why you are doing what you are doing and setting a measureable way ot know if you did that by the time you return. It doesn't have to happen on every run, but aim for 3-4 of your weekly runs to have a purpose.
Practice running faster - Tempo runs, fartlek, intervals, track. Whatever your method is, do speed work at least twice a week to get your body accustomed to running faster. When it comes time for the real thing, and you need to kick it up a notch, it will know just what to do!
Do double run days - 10km run in the morning, hills in the afternoon. Tempo in the morning, easy run in the afternoon. Double runs get your body used to running when it is not at its optimal, but you still need it to give a lot. Isn't this what a race is all about when you hit the last 10km?
Run lots of hills - Hills not only allow you to maintain pace on hills in a race when others may lose pace, but they also improve the efficiency of your body, allowing you to run harder without having to sacrifice later and slow down.
Do yoga - Whether its runner specific yoga, hot yoga, or just a weekly at-home practice, yoga helps improve your core, stretch and recover your muscles and enhance your balance and flexibility.
Strengthen your core - A good core helps with balance, good running form and improves running posture. Find some core strengthening exercises and do them 3-4 times a week.
Work those glutes - When your legs start to hurt, your glutes are the muscles that will help compensate and get you through to the finish. Practice exercises regularly to improve your glutes and see how much it helps your running improve.
Master your mental game - There will come a time on race day when all you want to do is quit and you'll have to convince yourself to keep going. Figure out what it takes to make that happen. Practice mantras, have a quote to think about, what ever you need to to get you through.
Figure out your nutrition - From your day-to-day nutrition needs, to your pre and post race fuelling options, practice what you eat during your running to make sure you are meeting your energy requirements and having enough calories to recover.