If law schools taught future lawyers how to bring in clients, how to develop business, how to cross-sell practice areas and how to offer a client more than they came in for, in other words how to sell, it would be the most useful education those students could receive. Nor would it be much of a stretch. Law schools already teach communication, critical thinking and listening. Business development is a natural extension of all three.
Besides, everyone is in sales. Students and lawyers looking for work are selling themselves. Firms recruiting talent are selling the organization. Litigators sell arguments to juries and judges. Transactional lawyers sell positions to clients and to opposing counsel. In-house lawyers sell opinions to the companies that employ them. Law school administrators sell their schools to alumni and donors, and to the students they hope will enroll.
Everyone is in sales, whether they wish to be or not. If law schools accepted that and included professional sales training in the curriculum, it would change the careers of a great many of their students.
Whether or not law schools ever take it up, there are practical steps you can take now to improve at business development. If there is a top rainmaker in your firm, ask her for guidance. There are also more books, classes and training programs on the subject than you could work through. Most of it comes down to a plan and the consistent execution of that plan. Start today. It may be the best career move available to you.