Tell A Story
Promoting and marketing anything can feel scammy at times. You're pushing people to buy, to invest, but you don't want to take advantage. It's a fine line to walk, but what's important is telling a story.
Whatever the product or service you are representing, find the story underneath. What is its purpose, why does it exist, how will it make someone's life better? Those may seem like deep questions if you're advertising a vacuum or some other "mundane" product, but you can still find a story. Look at recent ads for smartphones or tablets, emotional, personal, and moving.