Through my career as an agency creative director, I've often been asked for what I believe are good guiding principles. I just came across this list, drawn up some years ago. I think it holds true.

1. Be involved at the planning stage. It is important for the creative person to be contributing to and steering strategy prior to the briefing stage. Otherwise you have no right to complain about an unworkable creative brief.
2. Be an information sponge. Read all the research and collect information pertinent to the category and product all the time.
3. Research if done well is your friend. Creative testing is not.
4. Great ideas are the message. Never conceptualize with a particular media channel in mind. A great idea knows no bounds and owes nothing to any medium.
5. Know your audience. Study everything about them in order to reach them in their habitat, in context of product usage and in their language.
6. Hold no prejudice. Do coupons with the same zeal as you would a tv campaign. A banner ad or social media campaign might be the best thing you will ever do in your career.
7. Things are rapidly changing. Don’t hold on to yesterdays way of doing things or you will become part of yesterday.
8. People don’t change. Don’t confuse fads and trends with what motivates people. Inevitably people always want the same basic things.
9. Think don’t settle. When working on coming up with ideas, don’t settle for one – settle for one hundred. A creative person must totally surround a problem with solutions in order to quickly retire bad ideas and cultivate good ones. If you don’t, your competitor will.
10. Opinions only matter if you are in possession of the facts.
11. If your brand is not the market leader, make it the culture leader. If you do that well, in time it will become the market leader.
12. Where there is no imagination, brands perish. Create a story, a mythology, don’t create ads.
    
13. The law of parsimony rules. And reductionism is its vizier.
    
14. Great ads can be done for any product. Great ads cannot be done for idiots. Find great clients and work hard for them.
15. Turning down your ‘great’ idea might be the best thing a client ever does for you. It forces the smart person to go back and with added motivation come up with something even better. It also forces the hack to go back, bitch and come up with something worse.
16. Dig Deeper. Ideas and execution should be approached the same way. Dig down, look at the object from every angle, relentlessly pursue all possibilities (wouldn’t it be awful if somebody else, somewhere, was dealing with the same issue and they solved it better than you?) And then question everything. You are the judge and jury.
17. There are three kinds of clients: 1. Those who know. 2. Those who don't know and think they do. 3. Those who don't know and trust the judgment of those who do.