Try this approach if you have to go to a supermarket this weekend.
Decide to be kind, helpful and considerate to a fault. Let people push past, block the aisles, trail four kids around and dither over choices. Step back and let people in a hurry through, offer to reach stuff on the top shelf...
I have no sympathy for people queuing at petrol stations. It seems the vast majority still don't realise that petrol pump hoses will reach the far side of a car. So they will queue behind old folk even when there are free pumps or shorter queues.
Serves em right.