Google Keyword Planner is an effective way to find keyword opportunities.
It works best when you are actually suing the Ads platform though. When you do not have an active Ads account you can still see the keywords and the cost-per-click (CPC), but you do not get accurate data around search volume. Without using Ads you will get a range of keyword search volume, and those ranges are too long to make any real decisions on whether to target a keyword or not.
