Extracts from a manual written by David Ogilvy for AGA’s 1935 advertising campaign, that still hold true today (mostly):
There are certain universal rules. Dress quietly and shave well. Do not wear a bowler hat. Go to the back door (most salesmen go to the front door, a manoeuvre always resented by maid and mistress alike)… Tell the person who opens the door frankly and briefly what you have come for. It will get her on your side. Never on any account get in on false pretences.
In general, study the methods of your competitors and do the exact opposite.
Find out all you can about your prospects before you call on them… Every hour spent in this kind of research will help you and impress your prospect.
The worst fault a salesman can commit is to be a bore… and if you can make her laugh you are several points up.
Perhaps the most important thing of all is to avoid standardisation in your sales talk. If you find yourself one fine day saying the same things to a bishop and a trapezist, you are done for.
The more prospects you talk to, the more sales you expose yourself to, the more orders you will get. But never mistake a quantity of calls for quality of salesmanship.
The good salesman combines the tenacity of a bulldog with the manners of a spaniel. If you have any charm, ooze it.