Wangari Maathai was a Kenyan environmental and political activist. She said, "It's the little things citizens do. That's what makes the difference. My little thing is planting trees."
You can either plant a tree, or if that isn't your thing and you perhaps prefer more immediate results, then here is a brief sample list of 'little things' you can stop doing to make your personal contribution to society. I promise you will feel worthy, a spring will return to your step, and people will say 'there goes a good citizen!'
First and foremost, do not push aside any 'Baby on Board' passengers for that prime seat on the train. Do not then noticeably peer at the hauler of the 'baby on board' button to see exactly how far along that baby is when trying to gauge who deserves that precious seat.
Do not stand still and unyielding in front of an open door of a crowded commuter train as passengers try to alight or depart from the train. That is just obnoxious.
Do not tap your Oyster card once, twice, then take it out of your wallet, try again once, twice, and then decide to move aside for the increasingly hostile queue behind you.
Always stand on the damn right side of the escalator.
Absolutely do not push aside the elderly, the slow of foot, or tourists; and do not tut loudly when zipping past them on the street or a crowded train platform. Is arriving at your destination more urgent than everyone else?
When riding your bike in the city streets for commuting or pleasure do not ride in the middle of the lane. You are not a fast moving vehicle, you belong in the bike lane or towards the side of the road, and if you do not obey these rules we will lovingly nudge you with our car.
Do not ride your bike while on the phone.
Do not drive your car while texting or yapping away on the phone. Unless, of course, you are a doctor and you are saving a life while continuing to drive and talk on the phone - much to the annoyance and danger of other drivers on the road - then, by all means.
Do not speak loudly anywhere in public on any cellular device. No one wants to hear about your marital problems, your job woes, or your deeply personal medical issues.
Do not bring an oversized suitcase on a plane and insist that it will fit in the overhead compartment. It won't. You will lose the battle with the airline staff. It will slow us down from leaving. You will not be popular with your fellow passengers.
Do not glare at parents on a plane with small children. They are in more anguish than you can imagine.
Do not jump a queue - any queue, anywhere, for any reason.
Do not throw trash anywhere except in a bin. Are you a child? If you are a child, then still don't do it.
Do not complain about the weather. It rains in England. That's what it does. Let us move on from it.
I had a much longer list but for the sake of sounding like an absolute curmudgeon, I will stop there. In summary, I offer a quote from the 'classic' movie called Bill and Ted's Excellent Adventure:
'Be excellent to each other.'
However if you do chose the first option, please do let me know how well your tree grows.