A successful blog is defined by your goals, and your strategy to achieve those goals. You can have tens of thousands of hits on your blog, but if none of those people is the "right" audience for it, then it's not going to be successful for you. Quality over quantity wins every time.
If you haven't already, start by defining what it is you want to achieve with your blogging - is it developing a reputation as a thought leader in a particular subject area? Is it business development? Is it enhancing your professional credentials? Depending on what you want to achieve, you'll then identify who it is you're writing for, how to reach them, and then ultimately, whether you're being successful in getting traction with that audience. But "success" is more than just clicks on your blog.
What will be most important to you in gauging your level of success is how engaged your audience is, and this is a difficult thing to measure. The number of clicks that you get on any post is a measure of your "reach" — basically, how many eyeballs are seeing your posts. Either your blog host should be able to provide you with tracking statistics, or Google Analytics is an excellent tool to give you a look at the data that you need to see how people are interacting with your content. But unfortunately, that doesn't tell you much. It's difficult to know from those numbers whether someone has read your content all the way through, or spent any time with it.
You can look at the "time spent" on your blog, but that can also be misleading. We've all navigated to a website, only to be distracted by a call, or an email coming in, and left the browser window open - instances like that will artificially inflate those numbers. So the best metric, as per the Content Marketing Institute, is what they call "scroll depth." This tells you how far down a page a reader has scrolled, meaning that if they have scrolled all the way to the bottom, they have presumably read your content all the way through. Google Analytics doesn't measure this, but WordPress does offer a free plugin that will tie in with your analytics. You can also take into account how often your blog posts are shared, but there is quite a lot of data to suggest that there is actually very little correlation between what people read, and what they share.
Ultimately, you'll also need to tie these numbers in with other data, depending on the goals you've set - for example, if you'd like to be known as a thought leader, and being quoted in certain niche magazines and asked to speak at conferences is your goal, then connecting with people who can make that happen and getting those placements/opportunities will be a reflection of your success. Similarly, if your goal is business development, you might include a line on your new client form to identify whether your clients found you because of your blog. This, and other goals, can be harder to track, because the data is more subjective, but you can use a combination of metrics to review your content, see what's working and what isn't, and refine your strategy to continue in pursuit of your goals.
Lindsay Griffiths is the director of relationship management at International Lawyers Network with experience in branding and identity development, as well as supporting an international legal network of more than 90 firms. She is also the co-chair of the Legal Marketing Association’s Technology Committee.