I buy a bottle of bubble bath for £1 and put it into my soap bottles - no one notices
Use slightly less washing detergent that manufacturer recommends
Cut up old t-shirts and use them for cleaning
Regularly check fridge and cupboards and use up anything that won't last
Leftovers from dinner can be eaten for lunch or put on the side with tomorrow's dinner
Many shops over repeat, so I only buy certain things when they are on offer