We can learn from IBM. Every branch manager of IBM will always have a comprehensive file on each of his top 100 customers. These customers are termed as leadership accounts. Most of us keep this information in our heads. Reduce it to paper, review and call them up. Solve their problems and when you do that, these would become your opportunities. Please note that 100 is not a magic number! You can have 10 or 20 or 30, idea is to separate the `wheat from the chaff` and allocate your limited resources according to that.