Can't remember where I came across this.
Obviously thy want to sell you a course somewhere along the line(it will be a cold day in hell before i pay for anything) but there is a lot of good advice.
I really like the way it mentions the psychology of selling,it took me years to get any good at selling t a face to face customer(still not that good).
Pricing your Products for Wholesale

If you find anything really good,let me know.
I've got an aversion to reading more than a few lines.