HOWTO find great deals on codeshare flights

A Consumerist reader points out that you can save $300 on a $800 Virgin Atlantic fare from the US to the UK by booking it as a Continental codeshare. Consumerist explains how to search for deals like this:
So how do you find codeshares? First, find your desired flight number and punch it into a flight tracking service like Flight Stats. Look for a section breaking out specific codeshares and the flight numbers associated with the other airlines. Then, go to each airline listed and search for the codeshared flight number to compare the price. Once you've found the lowest fare, book it and start packing!
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