Here’s a list of things to double check to make sure your Shopify store's theme is SEO ready. It's not exhaustive, but if you follow it, you'll have a great foundation for your on-site SEO.
- Page titles and subtitles are present and marked up with header tags
- All images have alt attributes
- Description meta tag is present on each page and provides a sensible human description
- All pages include a canonical tag
- All product and article pages have appropriate Microdata attributes
- All product and article pages have appropriate Open Graph markup
- All product and article pages have appropriate Twitter Card markup
For more advanced reading, I highly recommend Gavin Ballard's Mastering Shopify Themes. Specifically check "Lesson 9: SEO and Social Integrations" for clarification on any of these items. This list, borrowed with his permission, was included as a supplemental material in his book.