How about...
planting tomatoes
How about...
turning off the tv
How about...
using the stairs
How about...
turning off the lights
How about...
using a cup when you brush your teeth
How about...
recycling cans
How about...
using the shower
How about...
riding a bike
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reusing plastic bottles
How about...
turning off the water
How about...
recycling paper
How about...
planting trees
How about...
using a cup