Recycle
Go out to the movies or restaurants less
Don't buy any new gadgets or gizmos (new cellphone every time a new one comes out or TV when your old one still works)
Don't replace anything like furniture or appliances just cause you want something new, "Don't replace what ain't broke"
Be content with most things you have now, don't go overboard on fish tanks and fish ( or anything else for that matter)
Grow fruits/herbs/veggies to save on food bills
Use coupons
Use energy efficient bulbs around your house
Install solar panels ( if you got the cash up front to invest in it)
Ride a bike or take public transportation instead of driving
Drive a more economical vehicle