I believe you learn more about your potential customer through listening to them than you talking would you agree?

I believe to crack a deal a sales person must be a active and good listener, good listening will enhance objection handling and will give more satisfaction to the client who has given a sales person his valuable time plus he will feel more special when his questions are listened and answered properly also this will ensure more and more closer steps towards closure of any particular transaction.  

I also totally agree.

But I would say that you don´t only need to listen - you have also to watch the customer.

I experienced so many times that customers tell only a part of their needs. But if you visit them at their company and watch their employees doing their daily business then you can identify some more needs and requirements of the customer.

I totally agree. The most common mistake committed by companies today is, to market and sell product features, rather than first listening to and understanding the problems faced by the prospective client. The very first step to setting a good impression is to make your prospect feel that we are here to understand his situation and then propose an apt solution to overcome the same. This also gives more insight on the outlook and direction of the prospect. More the client speaks, the more information you receive.