Shallow wells have a tendency to have a higher amount of bacteria in them.
- Pour a gallon of bleach down your well.
- Open-up each outlet in the house and run them each until you smell the bleach.
- Let each location stand for 3 to 4 hours.
- Now flush them until you don't detect the smell of bleach.
This article from the Water Research Center may help.
And if you REALLY want to get this right, review this video and take notes: