so, what are some of the things that "legit" companies do for SEO?
When my son was born I was looking for someone to take over my day to day tasks since I had little time to devote to my websites SEO as the day to day business activities took all of my time combined with having a newborn.
I hired a very well known top ranked SEO firm. I hired them on a two month trial basis in the 6 figure range ($120k to be exact). One month went by with 0 work done, they coughed it up to "research". I then found them posting WTB links threads on a popular webmaster marketplace. I was furious. They were giving me "advice" and I had to hold back from calling them up and cursing them out about how much they know about SEO.
So you have a good question, what is a legit seo firm? I really wouldn't trust any firm after my experience. After that I hired someone, gave him a salary and taught him everything I know. This way I know the job gets done the right way.
Well known SEO firms reach out to me (some find me on here from the threads I post) when they get stuck.
The SEO world is full with a lot of companies preying on unsuspecting clients who are sold on sitemaps, directory links and article submissions. They have a good sales pitch but that does not mean they know what they are doing.
I take great pride in what I do. I didn't learn what I know from some book. I learned the hard way through years of trial and error.
To get back to your question. A "legit" company will first and foremost focus on your sites content. They will pinpoint where your content lacks and where it can be improved. Unique content is no longer the key, anything can be spun to look unique, today there are many factors that make content "great" in the eyes of google. This means use of video, images, graphs and other features that are not offered on the competition.