1. Cook books are a wonderful and invaluable tool -- especially when you don't have to pay for them. (Some might not care for this step but It's what I do each month.) I usually go to a bookstore with a cafe or general seating. I take out cookbooks that look the most interesting to me. Then I take a seat and go through each book, writing down the recipes that jump out at me. Once I'm finished, I put the books back on the shelf and go on my way. Not only do you get great recipes, but you get great recipes for free. When every dollar counts, things like this don't sound so bad. I actually think it's kind of fun too!
2. Once you have a stack of recipes that you're dying to try out decide if you will be going grocery shopping for the week or month. (I usually shop for the month and it's my favorite day of the month!).
3. Pull 8 or 10 or more recipes from your stack if you're planning for the week and around 25 if you are planning for the month. Keep in mind that you will have leftovers.
4. Get a sheet of paper and go through each recipe card, writing down all the ingredients you will need . Do not write an ingredient more than once and do not write ingredients you already have enough of (Flour, olive oil...).
5. Now you have the bare bones of your list. Add any other random items you need and you have yourself a grocery list.
6. Sometimes if I'm feeling extra savvy, I will organize my list based on the grocery isles. (Dairy, grains, vegetables....) This can save you a lot of time in the actual store.
It is very important that you stick to your list! Do not get trapped by sales or things that just look tasty. Remember the time it took you to make the list and think of the gratification you will feel after you stick to it.