Communication During the Interview

It's not a secret that a big part of the interview is a test of your communication skills. Software engineering is a team sport.
The myth of the lone genius programmer is simply that-- a myth. This is especially for big, hairy, impactful projects that require hundreds of thousands of engineers.
How do you demonstrate strong communication skills?
You must keep talking - I can't emphasize this enough. Unless you need complete silence to think-- which is fine-- you should be voicing your thoughts.
- If you're stuck, let the interviewer know
- If you don't understand the problem, ask more clarifying questions
- If you have no idea what's going on, say you need more context
- If you need a hint, let them know!
If you're shy, that's perfectly fine. But with regards to the interview-- know that you might be working with either this person, or someone of a similar aptitude and technical ability. For better or worse, how the interviewer sees you during the interview is what they think they'll get when you come on board. Try your best to be friendly and vocal, if only for the few hours it takes to land the job.