To win the business development battle, you first have to make sure you are aiming at the right targets. Each one you miss wastes valuable, and limited, business development time and resources. As a result, the most effective targeting involves aiming at the targets that you have the best chance of hitting.
Start with your current Clients. Presumably they are already your allies, since they are currently writing you checks. To effectively develop more business with existing Clients, first prepare a plan of attack. Identify areas where they have needs that are not currently being served by your firm.