I check what is in the freezer, fridge and pantry and then I plan my meals ahead for the week. I also review and recipes I will be using that week and make up a list for everything I need on my computer then print out the list. This enables me to avoid impulse purchases, gets me out of the store faster and saves me $$
I also stick to the outer parameters of the store where all the fresh food is. I try to avoid buying processed food as much possible as these end up costing more money.
I check the weekly flyer for the store I normally shop at for any specials they have and check to see if I have any coupons I can use before I go shopping.
I also make sure I eat and have a coffee
before I go to the store so I won't be hungry and crabby while I am there