Bring plastic packaging back to the supermarket when you've unpacked your vegetables and fruit
Cycle rather than driving for all journeys under 5 kilometres
Grow at least some of your vegetables - for instance the super-easy Daubenton's Kale, a cottage kale that propogates by your taking off and planting side shoots and rarely comes to flower
Use your dishwashing water for watering your flowers and veggies
Put your coffee grounds around the hosta to keep away slugs
Instal a water butt to harvest rainwater (haven't done this yet)
Insulate your home as well as you can afford
Eat more vegetarianishly - for instance have one meal a week a veggie pasta and one meal a week a lentil soup
Hassle the hell out of politicians to cut your country's carbon footprint