"Form follows function" is a term most frequently heard in architecture, but it applies to your e-commerce website as well.
The better your product pages are laid out, the more they will be optimized for peak SEO performance. An infographic by Wired SEO illustrates 17 steps to help you through the optimization process.
From the title at the top of the page to the related-item links usually found at the bottom, the info that your pages include matters for SEO and conversions.
And don't forget to make your pages mobile-friendly, and ensure they load quickly, the infographic also points out.