Just the usual stuff........
Dairy and smaller items purchased from Costco/bigbox supermarkets. Sounds like a hassle, but hey, $2 difference on a 4 ltr (4 qt) jug of milk adds up pretty darn fast.
Purchasing local fruits. O.K., I'm not an a'la carte restaurant, but a chocolate and pastry place. Still when blueberries are in season, I buy local and freeze, when strawbs are in season I buy and make jam.
Don't see why you couldn't buy in local spuds, onions, etc if you had the space for them.
When I had the catering biz I got the shaft from the mega-bakeries, my deliveries were usually 2 dzn pullman loaves which was not attractive to them and they let me know it. Finally woke up and bought frozen dough, got my d/washer to pan it and proof it. True, I had to invest in used pans and a bread slicer, but my costs were waaay down. Don't see why you couldn't do this with burger buns or pullman loaves as well.
Now it's late Feb. Seville oranges are in season. How much money can I squeeze from one case of oranges? Usually 40 1/2 pint jars @$7.00 retail, and I still have leftover peels which I candy and use in my confections and bon-bons. Started to sell candied peel as well, commercial stuff goes for over $15 a kg.
Chocolate always increases in price, typically in 15% increases. I deal directly with the mnfctr, it's true I get the dirty end of the stick becasue my quantitites are minute, but I still get a better deal than with any supplier and I only buy in 6-8 mth quantities. Stuff's expensive, but dark choc. has a two year shelf life, and I move it in less than 6 mths.
Grow my own herbs. Did this while I ran my catering business too. Bayleaf, rosemary, thyme, marjoram are all dead simple to grow, and require very little maintainence. Not much of a foodcost breaker, but it makes a noticeable difference, a lot of people do notice.
All this is labour. Can't have your cake and eat it too. But with me, there's a difference:
I'm a Mom & Pop outfit, No F&B or GM on my tail threatning me to do the impossible. I can also attract culinary students for 2 week stages--no salary, full insurance coverage, but for the first week I'm babysitter and yet by the second week I use them to fill up my freezer and shelves.
If you are independant you have the luxury of being creative, if you're corporate--I wish you all the best luck...........