"Conclusions are always based on cost per customer or cost per dollar of sale."
"The only purpose of advertising is to make sales. It is profitable or unprofitable according to its actual sales."
"Would it help a salesman sell the goods?"
"Would it help me sell them if I met a buyer in person?"
Act if you were trying to sell to a single half-sold person in front of you: no loud text, no restriction in length, no fioriture, no joking around.
"The more you tell the more you sell" – use 100% of the space for selling purposes, including with illustrations.
"The purpose of the headline is to pick out people you can interest."
"When you once get a person's attention, then is the time to accomplish all ever hope with him."
"In one reading of an advertisement one decides for or against a proposition."
"In every ad consider only new customers. People using your product are not going to read your ads. They have already read and decided. You might advertise month after month to present users that the product they use is poison, and they would never know it. So never waste one line of your space to say something to present to existing users, unless you can say it in your headlines. Bear in mind always that you address an converted prospect.
Any reader of your ad is interested, else he would not be a reader. You are dealing with someone willing to listen. So do your level best. That reader, if you lose him now, may never again be a reader."
"A man interested enough to buy a car will read a volume about it if the volume is interesting."
Use art only if it can sell strictly better than the same amount of text (or any other content in the same space)
"The probability is that [art] repetition is an economy. We are after new customers always. It is not probable that they remember a picture we have used before. If they do, repetition does not detract."
Don't advertise for the benefit of others.
"We cannot go after thousands of men until we know how to win one."
"People don't quit habits without reason."
Don't be cheap – being cheap is expensive.
Free is always incredibly powerful. "Before a prospect is converted, it is approximately as hard to get half price for your article as to get the full price for it."
"Give sample to interested people only. Give them only to people who exhibit that interest by some effort."
A/B testing
"People who buy through casual recommendations do not often stick."
Always focus on the positive and never badmouth.
A company/product name that can be trademarked and build brand value is a definite asset in the long run.