Grocery shopping - budget realistically, meal plan to ensure you don't need to pick up extras. I always buy way more than necessary when I go to get one item. For the basics I generally buy homebrand and try to do that as much as possible. Bake as much as possible for snacks etc as it is much cheaper.
I don't buy stuff we don't need and try to get as much on sale as possible. Definitely takes a while to get ahead too. Good luck!