How can you know about your SEO campaign whether it is working or not?
 

First of all I would attempt to make a search on all search engines employing relevant keywords and keyphrases, I am optimizing for. The analysis of results will say whether the methods of optimization have gained results or lost. I would analyze the report regularly as search engine makes updating and index. I would attempt to another aspect of website statistics which says about origin of traffic.

If you see that the number of organic keywords on your website are also increasing, it's safe to assume that you are targeting the correct keywords for your industry and using them successfully in your content.