Learn the business. One of the values of an in-house lawyer is to understand a business and its legal principles. 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.