I also shop the Wednesday ads, make a list of the things I need and buy often, then head to Wal-Mart (either very early in the morning or very late at night) and I take advantage of their price matching program. More often than not they have the items on my list for cheaper than what the grocery stores have them on sale for anyway.
Also, I've created a price list to reference in general but at Sam's in particular. It was a pain to create but I tracked everything I bought for a few months and noted the price that I paid. Now, when something is on "sale" I can easily tell whether or not it is a really good buy and when I go to Sam's for bulk shopping I know whether or not it is worth the space in my pantry (I've found a lot of stuff these days is actually more expensive at Sam's than if you just wait for a sale at the grocery store). And I ALWAYS do the math on sale prices. I've found that a lot of times stores will advertise items as "3 for $5.00" or something - and it actually works out to be regular price anyway (and I know because of my handy, dandy price list!). If I do find something that is a great buy I stock up as long as it is something that isn't going to spoil or can be frozen.
Also, for me, planning is key. I make note of what I have on hand and make my menus based on that and the sale ads. I usually make a week's menu to go by but I also think about a month ahead as well and create a sort of outline for those weeks too (making use of planned leftovers, bulk items on my list, etc.).
Oh, and I almost never buy prepared meats. For instance, I buy the bone-in, skin on split breasts and clean them myself. I can buy them for .99 a pound (and have gotten them as low as .79 a pound), the resulting breast is much bigger than the boneless, skinless breasts you'll buy in the store (2 is enough to feed my family of 5 - my husband I split one and my three small children share one - they are THAT much bigger!), plus, I can seperate the tenderloin and freeze them seperately to use in stir frys, for chicken strips, fajitas, etc.
Finally, I often make double recipes and freeze one for later. It doesn't necessarily save grocery money but it does save me time, and usually doesn't require nearly as much energy to heat up as it would to cook. So, if I do it often enough I see a slight difference in my electric bill. I even do this for things we put on the grill. I prefer charcoal grilling over gas and there is always plenty of heat still going once I've finished cooking our meal. So, I'll throw something else on and then freeze it. Later, I just have to finish it off in the oven (depending on what it is I might not cook it all the way through. This gives us the grill taste without drying out the meat).
I used to spend as much as $600 a month at the grocery store - sometimes more if I was out of staples like flour, sugar, and condiments too. Now, I spend as little as $70 a week and rarely more than $100. And the best part is that we eat good, healthy food. It drives my sister crazy because she only has 3 in her family and she spends at least twice as much as me on groceries and doens't eat nearly as well - they'll be having hot dogs and and we'll be having steak! She finally went grocery shopping with me last week to "see how it is done." It is corny, I know, but I've actually come to entertain myself by seeing just how little I can spend. What can I say? I'm easily amused.