Congratulations on your 500th sub! I too just earned my 500th sub yesterday. Best method? From what I can tell for this year, it's been putting out content consistently every month. I've set a goal for a minimum of 2 vids per month as that is about what my time allows atm. Additionally, I've been spreading my brand by going to social media, participating with other YT'ers from my niche/genre, etc. It's all helped. I don't know if there is ever a best method since we can't control people to click the sub button. We can only try to convince them through the content we produce. Is it informative? Is it entertaining? Is it good? Is the lighting and sound and editing good? So many factors.