Network optimization, how to choose keywords?

First, how can appropriate keyword indexing "degree" of it?
Either directly extracted from the subject noun, or small title, body, or taking part in summary terms, to apply the "degree" must be marked single concept, should not compound concept, and therefore we selected keywords, we must to the selected word or phrase defined. Such as "Alexa ranking query system source free version 6.0," a text, indexing the key words are: "Alexa Rank, Alexa Rank check, Alexa ranking query system, Alexa ranking query system source code, Alexa ranking query source, Alexa ranking source." The paper cited more than five standard combination of keywords, and five key words to form the title of the article, following the sensible and reasonable ...
Second, choose effective keywords
Keywords to describe your products and services terms, select the appropriate keyword is to create a high website ranking first step. Choose keywords is an important skill is to select those often used when people search for keywords.
Third, understanding keywords
Collect the required keywords in your before and understand how ordinary people is very important to use keywords. When people search is generally not a single word, but use the phrase or phrases. Choose good keywords for website optimization will play a crucial role!