My advice (and take it all with a grain of salt, I'm no professional) if you are planning on racing:
1. Subscribe to Runner's World magazine. My friend, Brooke, gave me a subscription last Christmas. It's a great magazine with lots of tips but mainly just inspiring stories. I usually well up with tears at least once during each issue.
2. Get professionally fitted for running shoes. Seriously, spend the money and do your feet (and frankly, the rest of your body) a favor.
3. Don't skimp on training. There are tons of training plans out there for every distance of race. Pick one or make your own blend. But get out there and run because if you don't you'll be much more sore and being sore is not cool. Before my Austin half in January, I did my "training" on the elliptical machine at the gym. On race day, my legs and feet took such a pounding that I was sore for a week. You train for a reason and that reason is so that when it's all over you don't want to amputate your legs.
4. Listen to your body. This was the most important thing I did during my marathon journey. During the last month, when my IT band and shin were bothering me, I had to pay attention to what things helped the pain. In my case, it was really cutting my mileage and resting my leg. It paid off since my leg didn't fall off and I was able to finish.
5. Enjoy yourself. I run slow. Seriously slow. But I can have a conversation while I'm running and I am generally not in any kind of pain. When I ran on the lakefront path, it made me laugh sometimes to see the looks on people's faces like they wanted to die. Slow down and smile. You should enjoy your running!
6. Celebrate your accomplishments. I think you should reward yourself for your hard work and effort. Eat that burger, drink that beer, devour that dessert. You earned it!
7. Wear a shirt with your name on it. And I'll holler at you if I'm watching. Which I totally plan to be doing at Chicago 2010, if you are shopping for a marathon :)
8. ANYTHING IS POSSIBLE! I'm not trying to go all Kevin Garnett or Jillian Michaels on you but I truly believe that you can do anything you put your mind to. I was the kid that had a doctor's note to not have to run if I didn't want to in high school. I had an amazing step aerobics instructor in college (and I realize how dorky that makes me sound but yes, Phys Ed was a required course and yes, I took it for a grade) that expected us to run 1.5 miles in 15 minutes as part of our final. It was an impossible feat for me at the time but instead of getting a doctor's note, I made up my mind to actually train for it and do it. And I got an A. I decided I wanted to do this marathon thing and I never allowed myself to think it an impossible goal. You may be sitting on your at your computer and thinking I'm insane but I believe that your mind is stronger than your body and trust me, a marathon is 95% a mind game. If you believe that you can, you can. That goes for life, not just running. Believe in yourself and others will believe in you too.