This doesn’t mean you shouldn’t trust legitimate SEO services such as site and index audits, which include site recommendations and fixes (both for the technical and editorial components of your site). You should expect clear expectations to be established before you partner with a SEO agency (or contractor) in terms of what type of support you are to receive from them.
Start with the basics for SEO. Have unique page titles and descriptions for each of your pages along with unique content per page. Use appropriate markup on-page and ensure that all of your page elements are appropriately optimized so that your site is accessible for those using screen readers and search engines understand embedded objects, such as images, video as such.
First off you should understand what the goal of SEO is to begin with and realize that it isn’t simply to achieve top rankings but for you to increase your online traffic with the targeted keywords; that deliver a rich on-page experience for your web-visitors with clear and actionable paths for them to take in either contacting via a form or placing a product to a cart for check-out. Your true goal is to improve your site’s content, structure and overall performance in order to capture more traffic which may convert to leads (new clients).