I thought I would post since I'm sitting here about to do the following. I always plan out my grocery shops the night before I go. It only takes a couple of minutes. First, I make a list of everything I need. I look through the coupons that I have randomly clipped out of the circulars and pull out relevant ones. Then I look at my list to see if there is any item that I could possibly search for a coupon for on the internet (Juicy Juice, Quaker oatmeal, etc.). I do my search and print stuff out. I put my list and coupons together and put it in my bag so I don't forget it the next day. The End :) I know it sounds rather involved but it's really not. I think its worth saving a few dollars on stuff you need anyway.
The day of my grocery shop I stick to my list. I save money by not going down any unnecessary aisles this way and picking out things I don't need. Sometimes I get lucky and an item I was going to pick up anyway has a coupon on the package. (Sometimes its better than the one I found, if I found one for that item).
Here's just some other random tips:
-look online and see if your grocery store allows you to attach electronic coupons to your frequent shopper card and do so before you go grocery shopping.
-some stores like Harris Teeter double coupons (sometimes they have weeks where they triple them) up to 99 cents.
-check the circular for the store you are going to to see if they have any deals on things you are planning on buying. This way you know which brands are on sale and which ones are the best price to buy.