well there are several options, depending on what is nearby you can look online, at a place called discount tire aka known as americas tire they have almost the same price as costco, these two stores were within a dollar per tire of each other. discount tire will match any price. Both stores have websites you can check discount tire has the best website, there is even a section for customers comments about the tires people buy, good or bad comments are included, once you pick the brand and tire size you like there will be a way to click for customers comments.
wal mart was about the next best store in fact some tires were better priced, and walmart has a large online store but if the price was better somewhere else, you could not talk to any one at walmart tires. Its a strictly order the size, pay and wait until the walmart store you shipped to called you. So actually going to the wal mart store is a better idea. Wal mart goes to big manufacturers, and makes deals, I got four michelin tires, they said wal mart on one side, in white letters, the inside said michelin. and they were pretty cheap.
There is an online store called tire rack.com They also test the tires they sell, and they seem to have some good prices occasionally, The one time the size I needed was on sale, I was not quite ready to buy, I went back later, and it was too late. So I ended up at costco. Tire rack had good prices, you have to add shipping to the cost of thres, and unless you want to drag 4 tires around, have them sent to a store near you, and then go down and have them installed. I do not know if there is enough savings over costco to make the hassle worth it.
Those are about the best deals out there. there are some rebates on some good companies now I see costco and americas tire keep good track of rebate information.