To chlorinate a well, dump a couple gallons of regular (no scented stuff) chlorine bleach down the well.You will have to remove the cover to the well to do this. Use 3 gallons if your well is more than 350 feet deep, and 4 if it's over 500 feet deep.
Run a faucet in the house untill you smell bleach. Repeat for each faucet. Once you have a chlorine smell at each faucet, let is sit for a couple hours, preferrably overnight. It wouldn't hurt to dump another gallon down the well at this point.
In the morning, thoroughly flush each faucet. also flush the well thoroughly, running it out the garden hose for a while, but try to keep the water off the grass or any gardens, it's not so good for them.
Like someone else suggested, it wouldn't hurt to flush your water heater once a year, but for different reasons.
I don't think I can open my well, can I?
Here's the whole well system:
http://i5.photobucket.com/albums/y181/Miztiki/Sept2006044.jpg
And here's the pump:
http://i5.photobucket.com/albums/y181/Miztiki/Sept2006045.jpg
There is nothing that I can identify that opens up to the well.
I will flush the water heater though. Thanks for being such a helpful FRiend!