HI Basically you should aware about your keywords that what type of services/ product you are planning to sell. Once you have a number of keywords which User will search than to know more combinations of those keywords you can use some tool. I will suggest for now to use Google Suggestion and Adword keyword tool for better understanding.
as far I know for best google watchword apparatus is 1)google adword tools.2)google incline instruments SAP Training Institute SAP Training
there are many keyword tools available but they won't help you to suggest keywords for your site promotion. you have to decide the keywords first then you can use google keyword planner to check search volume and keyword competition. keyword planner will suggest you relevant keywords also or you can take the help of seo company.
I have always used Google AdWord Keyword Planner so far, and the results are pretty good. I have confidence in that tool because I know who is behind it. And I cannot say the same for other similar tools.
We are using market samurai which is very good for keyword research. Moz keyword explorer is also best to use
The keyword search tools: These are the free tools: 1. Wordstream 2. Keyword Eye Basic 3. YouTube Keyword Tool 4. Übersuggest 5. Google AdWords Keyword Tool 6. keyword tool.io 7. keyword.io 8. lsigraph.com 9. keywordshitter.com 10. answerthepublic.com 11. Bing Keyword Planner These are paid tools: 1.Ahrefs 2.Semrush 3.longtailpro 4.majestic 5.kwfinder 6. similarweb
There is no best keyword research tool ever. You have to understand keywords value, search volume, competition, position, possibility and many thing manually. It depend on your niche and seo strategy. I think every web sites SEO strategy is different from another so keyword targeting should be different.