Where in the banner area of the landing page is the optimal position to place the call-to-action button to maximize click rate?
Exactly where to place the button is going to depend on a number of factors, including the level of interest of the visitor and the overall design of the page.
That being said, you generally want to position the button near the top of the page (and possibly repeat the action at the bottom of the page, if it's long), and make sure that it is adequately sized, has enough contrast, and enough spacing from other elements. Check out these resources for best practices and examples of good CTA buttons:
- "Call to Action Buttons: Examples and Best Practices" from Smashing Magazine
- "Call to Action Buttons" from The Landing Page Blog
- "60 Effective Examples of Call to Action Buttons" from DesignModo
Once you've got your basic layout in place, be sure to A/B test the heck out of it. There is no such thing as a universal truth when it comes to CTA buttons -- you've got to find the solution that works for you. For instance, Performable discovered that, for their landing page, a red button outperformed a green button by 21%. However, this result is not generalizable to different sites and different designs. Even a different userbase might result in completely different findings so test, test, test!