Get to the point. Nothing upsets a client more than an analysis of a problem with no answers. Wander the corridors. Valuable meetings can be impromptu. Avoid memos, communicate orally - don't be a bureaucrat.
Integrity is crucial.
Respect confidences and be honest and fair with clients and opponents. Make the coffee. Don't be too proud to do the mundane. Be a problem solver whether the question requires help outside the area of traditional legal advice or not. Hire people better than you.