I buy mostly frozen fruits, veggies (unless it's summer in which case I go to the very cheap and abundant farmer's markets) and chicken breasts.
I make a list and stick to it. I run down the snack aisles only to grab my fiance his favorite chips, and me my 100 cal packs. that's it! I've found when I linger in the snack aisle I spend $30 more on average!!
I check all expiration dates and buy the milk/cheese/yogurt/salad/ etc that will be around the longest. I hate throwing stuff out!
The only sales items I buy are the things I NEED. In the past I've spent more money buying things that are on sale just because they're on sale and a bargain. A waste if you never eat or use them! lol