Make sure that you go out and buy all of your necessary items for the two weeks ahead of time so that you are not wasting time and money by visiting the grocery every day or every couple of days. Stick to your list!! The biggest reason people spend too much at the grocery is that they buy things that are not needed, do not buy them. I am telling you, I can buy enough groceries to feed my family of four for two weeks and spend around $100 - $150. This amount includes organic milk and usually organic fruits and veggies, which always cost more.
Do not be afraid to substitute in any of these recipes. There are often nights that I will use different ingredients than what the recipe calls for and that is just fine. Use ingredients that are low in fat, dairy products do not have to be the full fat versions and this saves a ton of calories. If you do not like say black beans, but you do like pinto beans, well, use them.
Prep things ahead of time. I cannot stress this enough. I will chop and dice and slice ingredients a week ahead of time and then freeze or refrigerate until I am ready to use them. Doing this makes coming home and preparing a meal much more enjoyable and leaves me with my sanity.