This step is best done using a tool like SEMRush or Ahrefs because they have a tool where you can enter a competitor’s domain name, and it will show you all of its #1 rankings. Which is what we’re after.
However, if you don’t have access to these tools, then refer to your trusted keyword tool to identify the top 100 keywords by volume within your niche.
For this tutorial, I’m going to walk through SEMRush for this process. There’s a similar one with Ahrefs.
If there’s a big publisher who covers topics in your niche but also others e.g, goodhousekeeping.com, then on the main organic competitor's page, click on the number in the Common Keywords column for their domain. From here, use the filter to only see their #1 rankings and sort by highest volume first. Then copy down their top 10 that overlap your niche.