How to search and pick a niche ?

Be specific on how you want to monitize the yt channel. Is it the views you are after or the sales. If just views, then spot trends. There are various tools Nextlev, subscribr etc which are built specifically for finding and replicating viral content. And be active on the YT community on X to know what's going on in that space

Pick a niche that interests you and is in demand.

Create content for kids—it’s always relevant