Don't choose Sen Clinton as your running mate. Speaking as someone who used to support Sen Clinton's bid for the US presidency and no longer do. For one thing there is no chemistry there with Clinton... Sen Clinton and her campaign has called Sen Obama everything under the sun from incompetent to you know what. The press will have a field day with Sen Clinton trying to explain away the hypocrisy of a Obama/Clinton ticket. Not to mention what repugs have planned for her as being part of any presidential ticket ticket. She will be a drag on the message of change.
Sen Obama should choose someone who shares his beliefs and goals. Someone he he truly personally and politically compatible with. Personally I think Sen McCaskill is someone worth seriously looking at.
I just don't see any chemistry with Sen Clinton-zero. Yes I agree there are many policy similarities but that's were it ends. They will govern in very different manners.
Resist the conventional wisdom Sen Obama, it is almost always wrong.