A valuable tool for any webmaster is SEOquake, a toolbar and browser add-on that will give you useful insights into pages throughout the web. It works with Firefox, Google Chrome and Opera, and you can use it to learn all sorts of things about the pages you see including their page rank and keyword density.
SEOquake also offers a helpful tool for identifying niche vocabulary. To use it, identify a high-quality website in your niche. Use the SEOquake “keyword density” tool. This will automatically pull up and highlight recurring words and phrases. Make note of what these phrases are. When you go to another page in the same niche and analyze its keyword density, you should come up with a very similar list. Analyzing several high-quality websites within a given niche should give you a very clear idea of what related keywords are essential to discussing a topic.
You can use SEOquake’s keyword analysis tool to spot the difference between high-quality and low-quality websites within a given niche as well. Simply run a keyword analysis on an authoritative, well-respected page, then run the same analysis on a page on the same topic that does not rank as well. You’ll see quickly that the related keywords that are prevalent in the top-tier results will be lacking in the lower quality sites.
Using SEOquake on your own website or page will help you identify the keyword density and measure it against well-respected sites in your niche. This can help you see whether you’re on the right track and whether you need to make any vocabulary adjustments.