Mark J.

A lot of marketers and business owners don't trust folks in SEO because of operators like TopSEOS dot com.

I have direct knowledge of how they work. They charge for placement. They do not check to verify if an agency even DOES SEO, much less if they do it well.

DO YOUR RESEARCH.

SEO firms should be able to demonstrate success (check their clients' projects on semrush.com and see if they're getting decent organic visibility/traffic; call references; verify the experience of the individuals who would be assigned to your effort).

Good SEO should not be cheap. If it is, there is a reason that it is.

If you are unsure about someone, do not go blindly into an engagement. Do not start cutting checks to an SEO firm until you have a firm grasp as to how you are going to make money from the effort, you understand the approximate scope, you understand how much of an investment you may need to make until you are ROI positive on the effort, and you have the financial situation to fund it without freaking out (and the patience for the process).

SEO can work extremely well and drive tons of value. SEO is, however, "work" and it's work (and strategy) that needs to be driven by experienced practitioners.

You most likely will not find these types of individuals/firms listed on TopSEOs.