1. Saying "Hi" to a co-worker you run into on the way to work
You're going to be in the same area as they are ALL DAY. If you guys really have anything to talk about, I'm sure you'll do it by the watercooler or wherever people with real jobs talk about stuff. For now, just let them finish up their podcast or listen to whatever's on Pandora.
2. Holding the door for someone who's more than 6 feet away
If you see someone over 6 feet away, just don't hold the door for them. Seriously. They're not asking you to do it, and it's gonna force them to hurry up so they don't feel bad. Everyone walks away from that situation wishing you woulda just walked in and let the door slam behind you.
3. Stopping your car and waving a pedestrian across when you have the right of way
Listen, we set up the traffic rules for a reason: so stuff like "politeness" wouldn't be a factor at a 4-way stop. But when it comes to crosswalks, just follow the lights - a pedestrian looks like they wanna walk across the street, but you - the person in a car who has a green light - is letting them walk past? You're going to confuse them, they're not gonna walk immediately (if at all), and you're going to piss off everyone behind you.
4. Recommending a TV show
Since TV shows mysteriously got REALLY good sometime in late 2004, everyone's got a show to recommend (and it's always The Wire). But here's the thing - most people have access to a lot of streaming outlets that have ungodly amounts of TV shows on them, and their backlog is already bad enough. Don't pressure me to watch The Americans! I'm still catching up on Friday Night Lights and The Shield. I don't need to feel guilty about not watching ANOTHER powerful, immersive, hourlong drama. If I want a TV show recommendation, I'll do what any normal person does: ignore that impulse and watch a bunch of reruns of American Dad.