There is a short article on Seth Godin's blog about how Clueless Marketers still are.

How can you keep from becoming a clueless marketer? Follow a few simple steps.

1. Don't Always Follow the Herd
A common practice when writing copy is to see what others are doing and improve upon it. Analyzing your competitor's ads is one step in the process, but you also need to tailor the ads to your client's website. You also need to test different creatives to see what works best and build on those. Just because everyone else is doing it, doesn't mean it is the best.

2. Get data, Analyze it, Use it.
There is lots of data available. Collect as much data as you can and organize it. Analyze the data - look at it from different angles. Come up with a strategy backed by the data and begin implementation. Track the results, make necessary improvements.

3. Test
Sitting back and being satisfied with good results is the quickest way to be surpassed by competitors. Keep testing new ideas/strategies/etc. to optimize and maximize an account. Search marketing is a continuous process that needs to always be modified and improved.

These are three important parts of the big picture - there are still many more.