The biggest advantage any one provider has over another is experience and resource. The knowledge of what doesn’t work and what will hurt your site is often more valuable than knowing what will give you a short-lived boost. Getting to the top of Google is a relatively simple process. One that is constantly in change. Professional SEO is more a collection of skills, methods and techniques. It is more a way of doing things, than a one-size-fits-all magic trick.

As keywords define each page of your site, you can use them to organize your content and formulate a strategy. The most basic way to do this is to start a spreadsheet (your "content to keyword map") and identify your primary keyword for each article. You can then build your sheet to your own requirements, add keyword search volume, organic traffic, page authority and any other metrics that are important to your business.
Users will occasionally come to a page that doesn't exist on your site, either by following a broken link or typing in the wrong URL. Having a custom 404 page30 that kindly guides users back to a working page on your site can greatly improve a user's experience. Your 404 page should probably have a link back to your root page and could also provide links to popular or related content on your site. You can use Google Search Console to find the sources of URLs causing "not found" errors31.
Domain authority is an important ranking phenomenon in Google. Nobody knows exactly how Google calculates, ranks and rates the popularity, reputation, intent or trust of a website, outside of Google, but when I write about domain authority I am generally thinking of sites that are popular, reputable and trusted e.g. are also cited by popular, reputable and trusted sites.

TASK – If running a blog, first, clean it up. To avoid creating pages that might be considered thin content in 6 months, consider planning a wider content strategy. If you publish 30 ‘thinner’ pages about various aspects of a topic, you can then fold all this together in a single topic page centred page helping a user to understand something related to what you sell.

One common scam is the creation of "shadow" domains that funnel users to a site by using deceptive redirects. These shadow domains often will be owned by the SEO who claims to be working on a client's behalf. However, if the relationship sours, the SEO may point the domain to a different site, or even to a competitor's domain. If that happens, the client has paid to develop a competing site owned entirely by the SEO.