The scientific method changed everything...except maybe marketing.
Francis Bacon's innovative way to catalog and organize cause and effect enabled humanity to reach the moon, achieve self-government, and enable each generation to live longer than the last. It's simple really: state a hypothesis, identify a way to test it, carefully document the results of your test, analyze the results of your experimentation, and draw conclusions.
Why should building a website be treated any differently than anything else in the realm of science? We should make a hypothesis for what the website will achieve. We should identify a way to test those achievements. We should document the results of our test, analyze those results and draw conclusions.
What will your new website achieve? What will your marketing achieve? How will you measure it? How will you analyze it? And how will you learn and apply the results of that analysis?