My 6-point summary of Marshall and Todd's Ultimate Guide to Google Adwords:
1. Formulate a first version of your business hypothesis.
2. Identify potential customers and talk with them; understand their business processes, their goals, their pain points.
3. Refine your hypothesis to what your customers actually need.
4. Develop and optimize Google Ads that speak to pain points.
5. Refine sales process based on Google Ads lessons (what makes people click?).
6. With a robust Ad-to-Sale process, scale up with Google tools, social media, and email marketing.