If both you and your client expect to reach even greater levels of success, then you must have a strong and harmonious relationship between the two of you. Here's some advice on how to really make that investment pay off.
Most people answer relationship building.
I believe consultative selling creates the foundation from which profitable relationships are born. Relationships will get you the appointment, but the consultative selling approach will get you the business. Once you stop acting in the consultative selling mode, you start taking the relationship for granted. You stop doing some of the things that made you invaluable- the things that got you the business in the first place. I'm talking about creating a kind of relationship that instills trust and confidence in what you can do for them.