Keep a list of everything in your freezer & check it before you go shopping. Do the same for the fridge & stick the list to the front with a fridge magnet!
Using your fridge/freezer contents list, make a menu plan once a week. If you've got your store cupboard essentials you should be able to avoid any extra trips to the supermarket!
Save freezer space by using bags instead of plastic containers. Also, don't forget to label things carefully with that days date & the contents to avoid having to play any guessing games!
Line the salad drawer of your fridge with a teatowel. Change it weekly & it should help prevent any nasty slimy build up!
Bulk out meals with beans & pulses or even tinned potatoes. All are great value & can stretch out dishes to feed more!
Stop buying expensive bottled water & invest in a water filter jug. They are better for the life of your kettle as you will get less limescale build up. You can pick one up for as little as £8 with filter cartridges at about £5 for a pack of 3 (Wilkos).
At the same time why not get a reusable bottle to take out & about with you. You can get them for about £10 from Amazon. I use mine daily & it keeps the filtered water lovely & cold!
Do a fridge check once a week to see what is about to go out of date.
Try & make it a priority to use these foods first to avoid waste.