I've been working at a grocery store for over 2 years now (I'm 16 years old) and I've come to a point where I'm so fucking angry at these three groups that I had to write what I want to say to them.
Here's some easy ways to get fired from a Grocery Store (unless you're in a union, in which it's impossible to get fired unless you steal stuff or make a bomb threat).

60-80 year-old women
Consumer: What do you mean I have to pay for resuable bags? This is outrageous!
Employee: Fuck, oh my god, we've had big green fucking signs up for the past 4 months and your dumbass can't figure out that we no longer sell plastic bags. For fuck sakes, do you live to annoy the shit out of everyone you come across? I used to respect the elderly, but ever since I started working here, I've realised that you people care way to much about simple fucking concepts that somebody put ten minutes into coming up with!

12-15 year-old skater boys with rich parents
Employee: Get those wood planks out of here you little shits! Every other day you spoiled, mumbling retards come into my workplace and fucking annoy the shit out of everyone. You walk around dressed in your hollister and abercrombie, thinking you're fucking deprived and hardcore, well guess what you little shits, you're just as gangsta as the nerdiest guy in the hood. I will personally beat the shit out of everyone of you right now and if you assholes even try to hit with me with your expensive ass boards, I will break them in half and use the wood to burn the shitty little grin off your ugly faces.
And stop wearing winter hats during the summer in 85 degree weather!

30-45 year old women
Consumer: Excuse me! Don't pack my bread like that!
Employee: Why don't you shut the fuck up you uptight cunt! I don't give a shit if you're kids are annoyingthe fuck out of you and everyone around you! Putting bread with bread is not going to squish your bread bitch! Tell you're fucking kids to shut up and to stop asking if they can buy Beverly Hills Chihuahuas, it's a shitty movie and it's a god damned joke that they think it's worth 20 dollars.