[frewsxcv]

List your interests/hobbies/favorite things. Chances are, there's a subreddit for each of them.

[archagon]

And going one further, each topical subreddit usually has a couple of higher quality spinoffs. For example, r/gaming vs. r/games, or r/askreddit vs r/askhistorians.

[pavel_lishin]

And going further than that, there's spinoffs that appeal to an even more niche audience. For example, r/gaymers and r/asksciencefiction