Pretty important question, right?
Good news! There are a huge range of services out there that you can plug into your website to help you understand where your visitors are coming from, what they are doing when they are on your site, and how you can (at least try) to get more of them.
Every run of these tools will promise you the Earth in terms of SEO but remember – they don’t have any special insight into your website that you don’t have. Every analytical platform relies on data being passed to them by your website. They can only work with the data you give them and so, in reality, they aren’t telling you anything you don’t already know.
What good analytics platforms do do is help you marshal and interpret the data from your website and, hopefully, turn it into actionable insights.
Despite this all being pretty logical, I’ve seen websites running tens of analytical and tracking platforms simultaneously – utterly ridiculous.
Personally, I like to keep things simple and use a small set of tried and tested tools.
There’s no point running more analytical platforms than you have the time and skills required to monitor.