1) When you buy a jacket or skirt and there is a vent in the back, you are meant to snip the little diagonal or "x" shaped thread. It's called a vent because it vents. If you leave it closed what do you really think it's doing for you? Do not get me started on people who leave the tag near the cuff on their wool coat.
2) When the man and his pregnant wife in the elevator are taking about his job interview tomorrow for which he needs a suit, and he says he will "just go to H&M in the morning," close your mouth. You look stupid staring at them all gaga and horrified while they are perfectly happy: the guy, the gal and the kid they will probably name Maddysyn Caleighe McKenna or some such.
3) When you are back from your sartorial superiority-complex-inducing trip out of the office for lunch and get the email from school detailing how you need to: sign the teachers card, leave money for a gift within the "official school teacher gift guidelines" (link handily provided), sign up for a volunteer shift at the end of the year party (volunteering to bring food or prizes to the party does not, in fact, get one out of shift-taking responsibilities), bring money to the end of year picnic (NOT to be confused with the end of the year party, btw) to spend at the end of year book sale, send a $1 for the kid to buy a cupcake at the end of year kickball game (proceeds going to Africa or some such worthy place, of course), spend the day before the last day of school with your kid in the classroom to "share their experience," and attend the last day of school assembly from 8:30 - 9:30 am...do NOT lose your shit when you get to the part where you are meant to take your child home for the summer at the end of that 8:30 - 9:30 assembly. You will be tempted to do a cost-per-day tuition analysis and rant about the "last day" of school being hardly a "day" at all.
No one wants to hear it. And the other mommeighs at the end of the year picnic will be better dressed than you, anyway. They know full well what a vent is.