One more tip I picked up from TED talks ... power poses. They say not to cross your arms across your chest, don't cross your legs even. Stay "open" because it appears more powerful. No slouching in the seat, don't let your chest cave in. Sit tall.
It was really hard for me not to cross my legs, as that always seems so normal to do. But I actually walked in feeling more confident and powerful, because it sends a message to your brain that you *are* powerful somehow.