Coupons are awesome, there's no denying that! Sometimes, though, you don't have time to collect coupons, or you need to buy some staples to fill your refrigerator or pantry. Don't feel guilty that you can't use coupons on some of these staples -- there are plenty of foods that are priced right even without coupons (and even better with, when you get lucky!), and that won't often be part of a coupon deal anyway.
Eggs are nutritious and can go in just about any recipe without trouble, so purchasing eggs is always a wise endeavor. Occasionally, stores will have two-for-one sales, but that doesn't usually involved a coupon, and unless you get a really impressive special, you won't likely get any sort of deal on eggs. But they're reasonably priced to the point that you won't really need to hunt down a coupon, so buy away.
Rice is rarely on special either, and when it is, it's usually a sale as opposed to a coupon. Rice is such an inexpensive commodity anyway, though, that you really don't need a coupon! If you prefer to get a high-quality brand of rice, something that stores only sell in small amounts, you may be able to track down a coupon; but if you just use rice in bulk and are willing to buy the store brand, you can get a lot of rice for much less than a lot of foods with a coupon.
Canned food is an excellent staple to have, both just as a rule and in case of emergency. Name brand canned foods will often have a manufacturer's coupon for them in the paper, but despite having these coupons, you'll often find that the store brand -- which is just as good in quality -- is cheaper even without a coupon. So unless you're particular about the brand of your canned food, especially vegetables, it's probably better to just stock up on the store brand.
In general, the store brand of any product will be a better deal, even when you have a coupon (though there are some notable exceptions, of course). Often, the manufacturers use the same exact product, from the same exact batches, in the name-brand products as in the store-brand ones, and you're only paying for the label. So unless you're getting a significantly better deal with the coupon, just go ahead and forego name for price.
Always check out online coupon sources before you go shopping! And don't forget another great online source -- GarageSaleCow.com, the nation's biggest garage sale website!