How to create backlinks?

I hope this post will help the other bloggers too, I suck at creating backlinks, I don’t even know where to start, my research took me to write for us pages or guest posting but I’ve heard it’s not good for your blog, I see that some of the new blogs that are like 4 months old have over 6k backlinks, can anyone shed some light on it please? I feel like my blogs are getting deindexed because I do not create any backlinks.