Doing keyword research provides the knowledge and reassurance I am choosing the right keywords and page topics before creating content for my website.
I use premium paid for research tool; avoiding free tools such as Google's keyword planner.
Typically I look for top of the funnel keyword opportunities with high search volume and low keyword difficulty.
I also reverse engineer competitor pages by looking at where they rank, how many other keywords they rank for and their backlinks to determine if I can provide a better page resource.
I would say the key to my organic search improvements has been creating page resources around these top of the funnel search queries.