Reduce food wastage. Use up leftovers in other ways, freeze extra portions for meals another day, etc.
When peeling veg, wash thoroughly beforehand and then things like carrot peels and onion skins/roots can go into the stock pot.
Heels of bread get made into breadcrumbs and frozen, to use later in stuffings/coating goujons etc.
We only put out the bins when they are full (fortnightly collection on each - recycling goes out approx. 3 out of 4 collections, but black bin only about 1 in every 5/6 collections, brown bin roughly once a quarter).
We send clothes, toys, books and equipment on to younger DCousins all the time to get reused. Lots goes to charity shops or clothing bins to get reused if we can't do that within the family/friends.
We've increased the insulation in the house over the years. We have also had temperature regulators on the heating for years, and keep the amount the heating is on to a minimum yet still comfortable - so it comes on for 30 minutes before we are due to get up, and kicks back in 30 minutes before we are due to get home, but we keep it low during the day (but if the outside is very cold, it will kick in to keep the house from getting TOO cold and harder to heat). It will also turn off if we've heated the house up by using the oven or having the stove going.
We changed the open fire to a closed, wood-burning stove a few years back - the same amount of fuel makes a heck of a difference to the heat in the room now compared with the open fire! It also means that less heat is lost up the chimney when the vents are closed if the stove is not lit - we used to have a chimney balloon up there all summer and during the week in winter as we generally only lit the fire at weekends, balloon did make a difference especially in windy weather where heat was just sucked up and out.
Also, wear enough clothes - layer up, wear proper clothing for the conditions, and don't strip to just shorts/tshirts in the depths of winter but wearing jumpers or thermal layers, keeping on socks, wearing slippers if shoeless indoors etc, all help to not feel cold and not need heating on so much.
Energy efficient lighting - LED spots upstairs are good and bright but use lots less energy, and turning out lights as we leave rooms. Solar lights with motion sensors in the garden, for path to the shed etc.
Rainwater collected in a butt off the gutters at the back, which is used mostly for watering the garden (combination of flowers and vegetables) but also for washing the car and washing salt off sailing gear. Has been useful to supplement mains water when pipes burst in bad snow a few years back - we had buckets of water for flushing downstairs toilet.
Cycling and walking rather than driving locally, where possible. Doing all the "jobs" in a planned route on 1 trip rather than separate trips or doubling back on yourself to get the shopping, dry cleaning, chemist, butchers......all sorted. Try to do "big" grocery shop once a week, or even less, rather than lots of small runs for a few things.
Use public transport from commute to work.
Wash at 30 degrees. Use white vinegar and some tea tree oil instead of conditioner in the washing. Line dry the clothes when the weather is suitable. Dry clothes on a rack indoors if possible, and keep tumble dryer use to a minimum.
Bulk buy things like washing "powder" capsules, and refill tubs. Same for soap (carex now do large refill bags), shower gel (L'Occitane same), and also food stuffs (I have glass containers for flour, pasta, rice, sugar etc and refill those from larger bags where those are better value - sometimes though the smaller ones are cheaper per unit so always check!).