******” Quote from Google: One other specific piece of guidance we’ve offered is that low-quality content on some parts of a website can impact the whole site’s rankings, and thus removing low-quality pages, merging or improving the content of individual shallow pages into more useful pages, or moving low-quality pages to a different domain could eventually help the rankings of your higher-quality content. GOOGLE ******
QUOTE – “So it’s not that our systems will look at your site and say oh this was submitted by a user therefore the site owner has like no no control over what’s happening here but rather we look at it and say well this is your website this is what you want to have indexed you kind of stand for the content that you’re providing there so if you’re providing like low quality user-generated content for indexing then we’ll think well this website is about low quality content and spelling errors don’t necessarily mean that it’s low quality but obviously like it can go in all kinds of weird directions with user-generated content…” John Mueller, Google 2019
QUOTE: “Sitemaps are an easy way for webmasters to inform search engines about pages on their sites that are available for crawling. In its simplest form, a Sitemap is an XML file that lists URLs for a site along with additional metadata about each URL (when it was last updated, how often it usually changes, and how important it is, relative to other URLs in the site) so that search engines can more intelligently crawl the site.” Sitemaps.org, 2020

QUOTE:  Each piece of duplication in your on-page SEO strategy is ***at best*** wasted opportunity. Worse yet, if you are aggressive with aligning your on page heading, your page title, and your internal + external link anchor text the page becomes more likely to get filtered out of the search results (which is quite common in some aggressive spaces). Aaron Wall, 2009

QUOTE: “The Knowledge Graph enables you to search for things, people or places that Google knows about—landmarks, celebrities, cities, sports teams, buildings, geographical features, movies, celestial objects, works of art and more—and instantly get information that’s relevant to your query. This is a critical first step towards building the next generation of search, which taps into the collective intelligence of the web and understands the world a bit more like people do.” Amit Singhal, Google 2012

QUOTE: “common with forums is low-quality user-generated content. If you have ways of recognizing this kind of content, and blocking it from indexing, it can make it much easier for algorithms to review the overall quality of your website. The same methods can be used to block forum spam from being indexed for your forum. Depending on the forum, there might be different ways of recognizing that automatically, but it’s generally worth finding automated ways to help you keep things clean & high-quality, especially when a site consists of mostly user-generated content.” John Mueller, Google
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.