If you've been running any more than 30 days, you will get to the point of wondering if there is anything you need to change in your diet. Not only if you are looking at losing some pounds but also to help in your performance. I'm not a registered dietician but I do know what works and doesn't work for me when looking at diet.
One good website to try is Dr. Weil. He's a lifelong guru in matters of food/diet and he recently sent out the Top 4 unhealthy snacks newsletter. See Link: http://www.drweil.com/drw/u/TIP03621/4-Unhealthy-Snacks.html.
Now if you are just getting started in looking at what foods to eat, there are books that have been written on the subject. But a better place to start is to eliminate those foods that you shouldn't be eating. His Top 4 are:
-Instant Soup (because of the sodium)
-French Fries (actually, anything fried)
-Soft Drinks (we're not talking about Diet, but Regular)
He gives a free newsletter that you can sign up for, it gives Daily Tips that can give you a chance to think about your diet, but the main thing to start is to think about what you're eating now. If you're thinking that eliminating all of the above would be too hard, try with just eliminating one of the them and building from that base. Remember, it takes 21 days for anything to become a habit, and finding the discipline to stop eating all of the above with help with not only your weigh but also your running performance.