Cut down on hot water use. Take colder showers.
Cut down on heating/cooling. Wear more or get used to the cold.
Unplug electronics not in use at the time.
Do not have lights on if you do not need them, for example when the sun is shining or you are just staring at a screen (might want to turn the brightness & contrast of the screen down for your eyes).
Get rid of the TV service. It is boring anyways.
No processed drinks, including juice. Water, teas, and tisanes are great and much healthier than HFCS crap.
No processed foods. Cook for yourself.
Only buy food at grocery stores. Look for the cheapest accessible grocery store (Trader Joe's for me).
When buying food, consider the price versus how many meals it will provide, not the volume or mass. A pound of nuts may be $5, but that will go a long way. A $3.50 pineapple by contrast is one meal (but fucking delicious occasionally

)
Do not snack.
There are plenty of free or cheap ways to get exercise. Run, dance, pushups...
Bike when possible.
Do not smoke so much cannabis that you build up a tolerance.