Over the years I've done a lot of sales (staffing/recruiting, consulting, application development, websites, etc.). Of course, most 'traditionally trained' sales people would now say, "Everything is sales" or "Everyone is in sales" but I digress.
There are a few books I've thought are the best. The first two by Heiman/Miller are
I have a document you can download (Conceptual & Strategic Selling notes WORD document ) that provides an overview with notes on these two books. The document includes things like:
6 Keys Elements to Sales (Analytical Tools)
1. Buying Influences
2. Red Flags/Strengths
3. The Buyers Perception of Reality
5. Ideal Customer Profile
6. Sales Funnel
3 Phases of a Sales Call
The Essential Sales Tasks
5 Types of Questions during the Sales Call
Another book I stumbled on recently is CustomerCentric Selling which I'm reading now.