Wikipedia: The term keyword in reference to Search Engine Marketing (SEM) usually refers to a word or keyword phrase (combination of words, such as 'Chicago Courier Service') used to find relevant and useful web pages.
Keyword selection is part of the process of search engine optimization, which also includes content, simple site design, well-written meta tags and page titles
Generates advertiser competition(# of advertiser worldwide bidding on each keyword relative to all keywords across Google; shaded bar represents low- to high quantitative guide), approx search value for previous month, and approx average search volume. Also suggests additional keywords to consider, sorted by relevance, with same information
Second option: website content. You type the URL of your web site
Search generates list of keywords grouped according to item. For example, for wheatbook.unl.edu, the list included wheat penny, wheat ridge, of wheat, wheat cent, whole wheat, and wheat. Each term has same info (advertiser interest, number of searches). So it’s not intuitive, but then neither are search bots.
You type a keyword and it lists the top searches for related phrases. “Wheat production” yielded a list of 11 terms, ranging from the most searches (44 for wheat production in the USA) to several tied for two searches each. My phrase, “wheat production,” was second on the list with 7 searches.
Page title (blue bar across the top). Titles should be meaningful (not catchy; that’s meaningless to a search engine), long enough to convey keywords, and should avoid hierarchical designations, such as chapter 2. These are meaningless to search engines too. Remember, each page should stand-alone (but still have links).
Document text: Repeat title keywords in first sentence, first paragraph. Also make sure your content resides just in one place. Also use related terms, other terms that people might search for. Avoid keyword spamming. Search engines are wise to this. This is the old way to “game” search engines.
Within links (anchor phrases) Make sure anchor text uses keywords and describes the site you’re linking to. Avoid linking to pages that are too deep in the site navigation structure; think flat.
Images (alt tags)
What doesn’t matter: Spelling, grammar, readability, visual emphasis (color, boldface, etc.), long documents, number of documents in your site, rate of change, site maps