From a mid-pack 10K runner who sometimes even places in her age group... 

1. Know the pace you want to run, and do your best to stick with it. Don't start out too fast, especially if there are a 5K and 10K starting together (which is common). Also a lot of runners get all wired up at the start and then sprint when the gun goes off. Don't worry,  you will pass a large number of them in the first mile or so when they get tired.

2. Know the race course before you start, especially if it has a lot of hills, or if it has any off-road stretches (trails, dirt roads, etc.).

3. Maintain a constant effort going up and down hills. Don't sprint up hills as if they were interval training.

4. Run your own race. Don't chase the competition (unless you are really good).

5. Some experts recommend negative splits (running the second half of the race a bit faster than the first half).

Good luck - 10K's are fun races! 

Congratulations on a race well run!

I don't have the Daniels book handy, but the online McMillan running calculator is also a good predictor, and it takes into account faster paces over shorter distances. The McMillan calculator predicts that a 51:13 10K (8:14/mile) would yield a 4:00:21 marathon (9:11/mile). If your goal is to finish under 4:30, you should make it easily.  

http://www.mcmillanrunning.com/mcmillanrunningcalculator.htm