Well, singles are consistently slightly flirty but never anything overt....always baiting for the "ego stroke".
Then there's the non-stop "resume building" for a prospective spouse. Guys doing "manly things" (except admitting to video games) and girls trying to improve their figure, appearance and reduce debts.
Married people don't do any of this. We tend to think "we" all of the time. We don't care about self improvement....really! We don't want more college degrees or reduced debt or increased savings. We are usually generous with compliments because it's a habit. We aren't constantly signaling "available " with somewhat flirty comments or manipulating for ego strokes. We look for activities that aren't so gender specific. We definitely have a high value on a good dinner and conversation. How trite is it for married guys to excell at barbecue(or cooking in general), care about lawn maintenance or shrubbery?
Married guys (the good ones) are all knowledgeable and involved about their children and know a lot about their discipline and achievements.
Where singles are ever ready to talk about themselves, married people talk about everyone and everything else except for themselves because their focused mindset is always outside of themselves.
I knew a single woman that had a huge strawberry across her face and neck and arms. But she was always pleasant and was the queen of bunt cakes...always concerned about feeding us during class. Out of everyone else in the singles class she was the first to get married. And she was up against three different "barbie" type women with impeccable dress, makeup, pedigrees and resumes. (I myself have never been interested in the cooking sort...I am a four star (French Mobile) five diamond class of chef . I can cook very well for two or two thousand. I personally have been a fan of the "smart girls" . (And it doesn't necessarily work out for me) So none of the barbies were to my taste.
But at any rate that should give you a starting point to begin noticing the differences.