Everyone will tell you the same thing "follow SEO best practices, page speed, backlinks" etc, which is same for ranking in Google as well. Those websites are harder to rank compared to Google from my experience. If you could get 100 organic visitors from Google for past 30 mins, you may get 1 from duckduckgo/bing. Thats the proportion we are talking about. So, if you are for Organic traffic you need to get traffic from Google first. At some point, I get a sense like they simply follow signals from Google itself!!