I do a five-week meal plan for our dinners, and prep our lunches for Monday - Thursday on Sunday.
In the beginning our slow cooker was a life saver! On days I knew we were going to be out all day, I threw something together in the crock pot.
Since then I have evolved and now my meals are planned out ahead of time.
Now the way I do the meal plan is pick seven meals, then draw up a rotation list of four meals per week (the other three are leftovers, restaurant, or throw something together on a whim).
Each meal is only repeated three times, so you're not having exactly the same thing week after week.
Figure out what you can do ahead (mix chicken and marinade ingredients together and freeze, make huge batch of pork taco filling in the crockpot and freeze in smaller packets) and which ingredients will stay good the whole month. Calculate out your shopping list for all the things you can buy ahead of time.
Shopping and prepping are a huge day, but a lot of your prep is done! Then week to week, all you have to do is purchase your fresh ingredients and get things out of the freezer.
I got started with a book called "A New Way To Dinner".
It teaches you that with a little prep on the weekend there is minimal cooking during the week - just combine ingredients.
They feel like fancy/sophisticated recipes but they are easy to throw together (e.g., cook pasta, stir in the tomatoes you roasted on Sunday and corn and basil and you've got "Penne Pasta with Blistered tomatoes and corn".
My daughters love it.