How can I choose a keyword for my website? How do I know, before writing a blog, that google will show the related ads and that the keyword will make money for me? How can I know about the search trend for some keywords. For examplel, if I have a couple of choices, how should I choose from any of them? What is keyword density?
Use the Google adwords, Google external keyword tool and google trends to work on various combinations of keywords. Look for the keywords with relatively less competition and more search volumes and increasing search trends.
I can suggest you to use semrush for finding the best keyword for your site. It can make different types of researches, with lot of information which can help you to make right decision. Keyword Density is the number of Keywords in an description on the total number of words in the description. for checking kw density I use seoquake plugin.