Impact, lack of preparation (warm up and stretching), and bad posture or running technique (shoes can also affect this) is likely to be the problem is.

Try to cut back on your running until your shins recuperate, perhaps give it a week and then see how you're feeling. Stretch your legs regularly, especially your calves, and it would also be a good idea to check out some books on running technique in the meantime. You can do some form of zero impact cardio to keep active.

When you start running again, pick somewhere else to run besides on concrete if it's possible. Cross-country is nice, a horse track is even better, and even a school/college track is better than running on concrete.

For about 10-15 mins run at an easy pace to get warmed up, then do some dynamic stretches for about 5 minutes before you're actual run. While your running concentrate on your breathing and technique more than trying to beat your last time.

You could get a heart rate monitor, they come in different forms now, I think the watch and belt kind is the most convenient. The heart rate monitor can help you set your pace/intensity accordingly and when to have a rest interval. Interval running is easier on your legs than a long hard run any day.