Successful employees know how to be introspective. It can be easy to see the strengths and weaknesses of other people you work with, but it's always harder to critique ourselves. If you're having trouble figuring out how you can improve at your workplace, ask a close co-worker or your manager for an honest review.
You may sit in a closed-off cubicle all day, but don't let this stop you from meeting and mingling with people in your office. Employees who are successful at what they do are more likely to have work-related and non-work related conversations with people around them.