Your secret tips about playing 3 at the back

Many hours spend in this game, Many trophies won, but yet i still didnt managed to play with 3 at the back at any team and it really bothers me.

I mean i tried many times, but i always had a feeling that it will never works out perfect and Im just wasting my team potential. So here is the question, what are your Secret tips, things, that you do, while playing 3 at the back? I have just started new save with Rapid Wieden and my main goal is to built a great three at the back team.

By Secret tips i dont mean general tactical advices or smth like that, I want yours tips and things that you have done in your teams that work out being gamechangers for you (like setting certain positions/players some special commands, most important types of players for crucial roles on the pitch etc)