Be sure google analytics is installed on your website in order to track the progress.
With google no longer reporting 90% of the keywords being used to get to the site the new metric of choice to track your SEO progress is landing pages. If someone doesn't land on the homepage odds are pretty good they searched something related to the page they landed on.
Additional statistics you might want to track is how many people are visiting your site, how long they are spending, where they are located, and the most popular pages.
There is an additional form of analytics that will let you know exactly who is visiting your site. This will exclude anyone on a standard ISP like Comcast or Verizon but will include any business with their own network. This can be a very powerful tool for B2B businesses.
Ask your new customers and clients how they found you. Think about having a standardized form of questions you might ask them to help you adjust not only your SEO plan but also your marketing plan as a whole.