First, you should create list of keywords, once you have full list of keywords then filter it and remove some unnecessary keywords. Below tools will help to find the best competitive keywords for paid and organic search.
Google Keyword Planner
When implementing keyword research you need to assess the sites which take the top 10 positions... In otherwords you need to examine their authority metrics like MOZ DA, Majestic CF/TF, the number and quality of backlinks, their use of on-page SEO (title, tags, description, content etc)... Once done you need to ascertain the level of work on your part to compete...
First I download the entire relevant keword list from Google Keyword Planner. I evaluate CPC, competition, and monthly searches.
After getting rid of high competition keywords that have a low CPC and low monthly searches, I will then evaluate front page results for every keyword and look for keywords that show social networks, youtube vids, or poorly ranking sites on the first page.
Sometimes I will do a keyword analysis for a few days before uncovering a decent keyword.
But then the numbers in KW planner fluctuate with users very rapidly so you really never know. It's why I started a brick and mortar doing local SEO. lol
If you already have a list of keywords, SEMrush or Keyword canine can help a lot!
After doing a keyword analysis, you should have some keywords that are profitable, but who knows what will happen tomorrow?