SEO is an ongoing process that you have to work on. Issues crop up, algorithms change, and if you don't keep tending the shop it can fall into disrepair.
It's not any different than any other marketing channel. It's just that too many people think it's set-it-and-forget-it.
Even I do sometimes.
I've mentioned previously that I started to readdress my own website's SEO issues that have accumulated over the pact decade. By sharing what I'm doing and how I'm doing it, you'll be able to improve your store's SEO.
One of the big factors with both ranking and the search result visuals are your title tags.
These are the HTML tags that are visible in the browser's title and tab. They are used directly in most search results as the link text and when you share content in social media.
One of the issues my SEO audit uncovered was that many pages had matching title tags. That's where the same titles were used on multiple pages.
These were especially common on my article collections but even a few important pages had them too.
That meant Google would have a difficult time understanding what each page was about and the pages would be fighting each other for rankings. As any Game of Thrones fan will tell you, too much in-fighting can cause problems.
Using the SEO audit I went to each problem page and updated its title tag to be unique. Some of them were paginated pages (e.g. Page 1 of 3, Page 2 of 3) so I added the page number in the title tag. That won't have a major SEO impact but it might make it clear to a searcher who finds the individual pages.
Usually Shopify is good about creating unique page titles but sometimes it'll create identical ones, especially if you have similarly named products/collections/pages. You can edit your page titles in Shopify at the bottom of most pages in the SEO Settings area. Here's how to edit those titles without an app, including a way to edit a bunch of them all at once.
Another SEO improvement you can make is to get your structured data in order.
Google has been working on Rich Snippets so I bet there's going to be more search enhancements coming out in 2018 for stores with structured data.
And JSON-LD for SEO is the easiest and safest option in the Shopify app store to automatically add that data.
Already trusted by thousands of stores, it's among the top SEO apps overall.