My parents were married 67 years, just a few months shy of 68 years when dad passed. They got married at 19 (mom) and 21 (dad). I've been married almost 23 years. My oldest sister celebrates anniversary #32 this year and my other sister will celebrate #26 later this year. So, my advice would be to find someone who's been married a long time and get advice from them! Because whatever my mom and dad were doing right, it seemed to rub off on us kids.
My mom always told me that the key to a long marriage was.... 2 tv sets. And for the record, all of us kids have more than 1 tv set.