"Best in the world," "lowest price in existence, " etc are at best claiming the expected. But superlative of that sort are usually damaging. They suggestion looseness of expression, a tendency to exaggerate, a careless truth. They lead readers to discount all the statements that you make

Scientific advertising has altered many old plans and conceptions. It has proved many long established methods to be folly

The product itself should be it's own best salesman. Not the product alone, but the product plus a mental impression, and atmosphere, which you place around it

Never be led in new paths by the blind

People will not be bored. They may listen politely at a dinner table to boasts and personalities, life history, etc. But in print they choose their own companions, their own subjects. They was to be amused or benefitted

Don't, to gain general and useless attention, sacrifice the attention that you want

Impressive claims are made far more impressive by making them exact