A quiet/calm home. No dramas, no door slamming, rows, no flouncing off, etc. Everything calm and on an even keel.
That was achieved by proper communication, no secrets, no half truths, and respect for each other.
I was always honest with parents about my feelings, school life, social life, where I was going/who with, boys, etc., which made a massive difference to my relationship with them, as everything was out in the open, all above board, no shocks nor surprises, etc.
We've tried to do exactly the same with our child - not hard as we were together for 10 years before getting pregnant so were used to a calm/quiet home, which our child just slotted into really, just took our lead and behaved as we did. Never had a moment's trouble with him! (Nor with OH, as I got him trained too!)