Are You Building a Landing Page?

How do you go from an idea to a completed product of a landing page? What is your eye for quality when it comes to judging how good or how bad a landing page is? Do you know how a video and images and graphics will impact page speed, user experience? Mobile? Do you draft a mock up for mobile and for dust top? Or are you just dust hop focused? Am once you do all this, how are you able to convey this information to the design team? How can you tell them where the lynk should go?