With so many SEO tips online, people forget that the basics are just as important. Without the right base, it would take a lot of links and authority to rank. The recent focus on content and content quality has people putting more effort into writing at the expense of everything else. Do not ignore the following basic parts of SEO:
To get pages ranked, they need to be in the index. If there are issues when crawling, not only do you lose pages from the index, you lose the authority from any of the incoming links. If you ever see a sudden change in ranking for a particular page for a consistent period, conduct an SEO audit with crawl tests.
The site structure is important from the perspective of the search engine. A proper structure requires planning and thought as it provides context to the spiders. For example a URL structure like /blue/ is not as informative as /widgets/blue/. The structure then helps come up with good navigation for the website.
When it comes to on-page Metadata like titles and descriptions, it is only the title that we know for certain that Google uses as a ranking signal. Having said that, you should put as much effort when crafting the description, as it is used for the snippet on the search results and is one of the things that a spider crawls. At this point, we do not know if Google does, in fact, use some of the other Metadata as a ranking signal, even in a small way.