Most of our shopping trip this week was low cost items like pasta, rice and canned goods which aren't quite so expensive. The fact we are a two person household also helps keep the overall trip costs down.
I build our grocery list as we notice we need something throughout the week, and then go through it again adding and removing items as I'm planning our meals for the week with our local grocery store's sales flyer guiding what we are having for the week. While shopping, I check the prices on everything in case there is a surprise sale on something we will definitely need. Doing this helped reduce our grocery trips to something manageable and reduce the amount of items that we have to throw out. And I never go to the grocery store hungry because if I do, I won't stick to the list.