I have been working on my personal website for sometime, I think I have been doing a good technical job, but, unfortunately I did a terrible job while structuring the website because I didn't care about the keywords I was going to use. Although it is my personal website, I'd like to mention the main objective is the blog of the website, so I'd like that the keywords were related to the content that it is in the blog, at present google webmaster tools is displaying a lot of keywords that has nothing to do with the content of the website, and some SEO reporting websites such as woorank says that the keyword optimization of the website is awful, So I have 3 questions:

• How to choose, set and use keywords while structuring a website?

OPTIONAL:

• which are all the methods and sources used by search engines to collect the keywords of a website?
• there are some high profile websites that aren't optimized on this as well, should I concerned about this anyway?, is there anything more important that I should be concerned about?

(if you want to see the website please check my profile)