The Google Keyword Tool has a variety of helpful features meant to streamline the keyword research process. By entering terms or phrases into the search box, the Keyword Tool allows you to build extensive, relevant keyword lists from one simple interface. By default, the tool displays Advertising Competition, Global Monthly Searches, Local Monthly Searches, and Local Search Trends for each keyword. Additional options allow marketers to show the estimated Average Cost per Click, Ad share, and Search Share.
They also seem to be getting this wrong often enough that I've got less confidence that the keywords that make up these groups really belong there. I recently tried to check the volume for the keyword [active monitoring] (the practice of checking on a network by injecting test traffic and seeing how it's handled, as opposed to passive monitoring) and the Keyword Planner gave me the volume for [activity monitor] (aka Fitbit).
3) KWFinder is one of the "newer" kids on the block, but it's probably just about the easiest way I have found to find new long-tail keywords quickly. A couple of things I like about this tool is that it allows me to create lists of keywords. So I can group up my different sites by lists and revisit them at a later date. I can export the data to CSV and start building out campaigns. It also keeps a nice scrolling list of the last 20+ keywords you have looked up. The SEO difficulty indicator comes in very handy as well! As far as ease of use goes, KWFinder wins hands down.