Make sure you check prices before buying items in bulk. Sometimes the cost is the same (or more) and the retailer is hoping you won't notice. The best way to buy food in bulk is from the bulk bins at your grocery store. You may need to look at organic/natural food section to find these bins. But buying in bulk helps cut down on excess packaging. Some places (or for some items) they do allow you to bring in your own containers (with you knowing the weight of the container to subtract), so take that into consideration because you will be cutting down even further on packaging.
Or just consider by larger sizes. There is much less packaging & materials used on a container twice the size. You get twice the amount of product for less money and less wasted materials. But just be sure you are going to use that product in the time. It doesn't make sense to buy larger sizes if the product will go to waste & you unnecessarily purchased a larger container.
Also beware of packaging at bulk stores like Sam's Club & Costco. Sometimes your “bulk” items are each individually wrapped (like paper towels) and then wrapped again as a package. You are not saving on packaging here. Look for items that are not individually wrapped & wrapped again.