Using the train, instead of the car will cut down emissions because the train will be used by more than one person unlike the car which is used by just one person.
When you are brushing your teeth you should turn of the tap to save water.
You should minimise food wastage as the food that is wasted globally could feed one billion people.
If you save electricity by for example switching off the charger when your phone has reached 100%. This means that less electricity has to be generated at nuclear power stations and this means that less carbon will enter the atmosphere.
If you limit the amount of meat that you eat means there is a smaller demand for meat to be produced and for animals like cows to be slaughtered. So the less cows there are on the planet the less methane will pollute the atmosphere.
By recycling litter, less rubbish goes into landfills and into the oceans. If the rubbish goes into the ocean fish may eat the rubbish without knowing and may possibly die.