Good copy is all about the reader
You should be on the side of your reader
All too often a copywriter will feel that he has to write nice things about his client, who is after all paying him a tidy sum. No. No. No. A copywriter's job is to keep his reader happy.
The first task is to persuade your reader to read the story
Obvious I know. But often ignored or overlooked. If your subject bores you, what hope is there for your reader? Good copywriters don't bore their readers.
Stories of what you did and the tone of voice you use are the only things that really set you apart
Every firm wants to be seen in the eyes of its clients as a bit special and different from the rest. Your competitors will have good people, good quotes, and good clients. But don't overlook the obvious: no one has done the work you've done.