You should never sell your morals or your ethics. If what you sell is at odds with your moral compass or is in some way unethical, don’t sell it. No matter what it is, and no matter how much you stand to gain, it isn’t worth your character.
Never sell anything in any way that might be illegal. You can make more money on the outside of a minimum security prison than the inside. Ill gotten money isn’t real money because it isn’t really earned.
Never sell something you don’t believe in. If you don’t believe what you sell will benefit the people to whom you are selling it, you are being dishonest. You won’t sell well, and your prospective clients will see through your incongruity. Go find something else to sell.
Never sell yourself short. Never sell to people who don’t value you and what you do enough to pay for it, or to treat you with respect and dignity. Never sell for people who don’t treat you with that same respect either.
Never sell something to someone who will not derive the value from having bought it. I’ve never understood why people would claim they could sell “ice to an Eskimo,” nor have I ever seen anyone who said such a thing sell. Selling isn’t something you do to someone.
Never sell someone less than they really need. If they aren’t going to generate the outcomes they need by buying less than they should, don’t take their money and allow them to fail. You are better off hanging in there and helping them buy what they really need.
Never sell someone more than they really need. When you put transactions above relationships in sales, you end up not having too many relationships. You also end up not having too many repeat clients, and are left with little to no wallet share.