One tool that has saved me a lot of effort in the grocery store and kitchen is a perpetual grocery list.
What is it?A basic list of the items that you need/want to keep on hand. Sorting by the layout of your favorite grocery store helps. (Of course, then the commissary goes and rearranges, but I can't seem to stop them from doing that!)
What do you do with it?Different people have different strategies. I print mine out before I go grocery shopping, run through it quickly and cross out anything that I have in sufficient stock. I then add my meal specific items for the week (meats, odd ingredients, vegetables that I don't buy every week.) If I'm feeling shoppy, I'll go through the local advertisements and pen a little mini-list on the back with special items to get at particular stores. Another way to use a perpetual grocery list is to print it off right after you fill up the cupboards and post it in the kitchen. Whenever you see supplies getting low, circle the items you need. Some people like to do a laminated copy with a dry-erase marker, but that is just too messy for me. On a good day, I actually walk around my kitchen and take inventory of the items on the list, other times I just print off the list and highlight/circle the things I know I need. The first method is more effective, the second is faster. I even keep a copy on a thumb drive because I have been known to accidentally alter the copy on my hard drive, and recreating the list makes me very, very sad. A low tech version is to use your old grocery receipts - hang them on the fridge and circle items as you use them up. The circled items should be the things that you need to buy the next time you go shopping.
Why do it?It makes grocery shopping faster and easier and saves by money by stopping you from buying duplicate items. (Who really needs two jars of curry powder?) Also, you will make fewer last-minute stops for "just one item," which saves time and money.
How do I start?I recommend you use an existing list and customize it to your needs. Look here http://www.grocerylists.org/ultimatest/ or here http://couponing.about.com/library/blgrocerylist.htm for samples to get you started. Save a sample list, print it out, and go through your cupboard to make it reflect them items you really buy and use. Every time that you need to buy something that isn't on the list, add it. (Unless it is really obscure, of course.)
Good luck - I hope you find this useful. It has saved me tons of time and money over the last few years.