https://adwords.google.com/ko/KeywordPlanner/Home?__u=9276839804&__c=3354215444https://adwords.google.com/ko/KeywordPlanner/Home?__u=9276839804&__c=3354215444
You can start with Market Samurai, it is not free but they have two weeks trial which is enough for you to test everything.
I’ve been using Keyword country (Keywordcountry.com) to reverse engineer upto 96% of my competitors’ profit keywords...I’ve had a play around with other tools too but nothing like KC...It offers a risk free trial for 7 days. If you don't like it... just bail out There is nothing to lose.
Google Keyword planner is a free keyword tool and it is effective too because it is based on Google search network.
Google keyword tool is best . now a days you make Adwords account then you use Google Adwords keyword tool Thanks
google keyword planner (is designed for adwords) ubersuggest (a good for long-tails) rank tracker (is a keyword tracker, but also takes keyword suggestions from a number of sources)
I have tried with long tail pro which you can get the best keyword results as it's paid make sure to utilize the first 10 days trial instead any free you can work on this tool
you can try squirrly seo (http://www.squirrly.co/). they have free account but also, paid account with more features. I use the free on, because I'm not publishing so often