While Choosing keywords i consider two main points 1). Competition 2). Search Volume Choose keywords that has less competitor and high search volume
During keywords selection and analysis you must have to keep in mind the following; -Search -Competetition -Site Theme [Free, paid, offsite, online etc.] -Not Too Generic -Relevancy
Also worth checking CPC. If people are spending money to rank, then it usually means it's a money keyword. Though you do have to use some common sense as well
I use Google keyword suggestion and get also the search result on search engine. Then I compute for the Keyword Effectiveness Index to see how effective to target the keywords.
Look at the amount of local traffic being searched for a keyword. Then look at the average CPC. This is a good indicator of how competitive a keyword is. Companies dont bid high for keywords that are not converting to sales.
I use Google Adwords by clicking the Exact Match to see the result and find out the search volume. It is hepful to do so.
I usually search for a less competitive keyword by searching them with google adwords and find out the search volume.