The search for keywords related to your Web site, and the analysis of which ones yield the highest return on investment (ROI).
Keyword research consists of at least three major steps:
(1) discovery – finding as many keywords as possible relating to your Web site. Online tools exist to speed up the discovery process by allowing marketers to search for related keywords and their relative search popularity.
(2) ROI analysis – finding the most valuable keywords for your Web site. The most generic keywords are the most widely searched, but also the most competitive, and sometimes bring mediocre conversion rates. Generally, phrases that most accurately describe specific qualities of a site yield the highest ROI.
(3) competitive analysis – analyzing the strength of competitors for potential keywords. Competitive factors include how attentive sites are to optimization issues and the number of relevant inbound links they have received. Clustered metasearch engines such as Ixquick and Zworks can provide a quick overview of the competitive landscape on any given search term.
Google: Keyword Planner – free keyword tool
SEO Agency Tools Price Comparison 2015
MarketingTerms.com (February 14, 2015)
Finding the Keywords That Will Help Customers Find You
ClickZ (October 25, 2000)