Using the Topic Areas is one great way. Also whenever a cross-posting is done, PieFed combines together comments across all of them, which is another great way to see some communities that you had not noticed before. You can also just browse by All and see posts as they come out, regardless of popularity - I've found several poetry and philosophy communities that way.
Tangentially I will add that the PieFed community listings tend to be handled far better than Lemmy's (using active rather than historical subscriber counts), while searching for posts or users or comments is easier in Lemmy (several highly confusing UX issues aside, like sorting comments can't be done, only posts). You don't need an account to use the Lemmy search tools either.
Welcome!! ๐ค