Chances are, if you run a website, you have done search engine optimization yourself. Or you might have hired an SEO expert to help boost your website ranking. But what was done and how does it affect your website's ranking in reality? How do you measure the result of the changes that were made. Algorithms used by search engines are constantly changing. What worked in the past might no longer work or may even do you more harm.
To find out if your SEO is effective, you will need to monitor your ranking periodically. You could google your site with relevant keywords each day, but who has the time? Or you could use a website like SERPS if you have a few hundred dollars to spare each month. But if you want to be cost-efficient, try using a free, open-source project as an alternative.
From their website, "Serposcope is a free and open-source rank tracker to monitor websites ranking in Google and improve your SEO performances."
It runs on Linux, Windows, and Mac (it uses Java). Install instructions can be found here.
You can install Serposcope on a server of your own (small cost) or on your own computer (free) that you use everyday. The obvious benefits of running it on a server is that it will automatically track your ranking daily, without your attention, even on days when you don't turn on your computer, and will also allow you to share it with others - granted you create an account for them as well.
It will become more and more useful over time, as you see the trends and the effect your marketing efforts and search engine optimizations have on your ranking.