With a dinner diary, you'll eliminate the front-end work. On the weekend, decide what you'll be eating for the week and write down the nightly schedule in a durable blank book. Coming home late on Tuesday? Plan on a simple chicken and rice. Band concert on Thursday? Make a double batch of chili on Wednesday so you won't have to cook. Once the lineup looks good, hit the supermarket.
The longer you keep it up, the more valuable the book becomes. (After six months, you can have as many as 150 menu ideas.) You can also use it for planning parties. Take notes on what works and what doesn't, whom you invited and who came. If you have wine remaining from your holiday party, jot down how many bottles―and how many guests you had―so you'll have less left over next year. Or so you'll have more.