Ken Wax has written numerous articles on selling and how to advance salespeople. 

His monthly sales column ran in VAR Business magazine for five years and has been running in TED magazine for over seven years. Several are linked below.

Salesperson Vs Camcorder

The 5 Levels of Salesperson

What Version Number Are You?

Helping Your Customers 'Get It'

Have a Seat, Now Buy

Seminars, Webinars -- What Influences?

The Right Words to Win

It's Different at the Top

Sales Calls: Comfy or Compelling?

Sales Presentations: Uphill Climb

Sell Against Your Company?

Walking in Your Competition's Shoes