I get asked this question a lot. How did I start? What do I eat? How did I cut things out?
I started by first cutting out all fast food. Once I had that down, I cut out buying all foods that came in a box like hamburger helper, then I cut out foods that contained HFCS and MSG, and wheat, then I began ADDING a lot of veggies and fruits and only shopping around the outside of the store b/c that's where all the fresh food is.
My husband and kids pretty much eat what I eat, except for nights like tonight when I always make breakfast for dinner and the kids get gluten free pancakes while I had grilled chicken breast and spaghetti squash and I'm making a Greek salad for my husband.
As far as meal planning...once I get my produce co-op I know what other fruits/veggies I need to fill in the gaps and I meal plan on Sunday using those items and meats/fish/chicken that I have in the freezer, and then I pull out my cookbooks and I involve the kids in meal planning. Especially my oldest. She's been involved in our cooking since she was 5. At that age she looked through cookbooks for items she'd like to eat, and would write them down (helped her with her handwriting too.) I food prep on Sunday for the week. I grill chicken breasts, etc., things that make it super easy for me to grab and re-heat, or grab and go!
It was (and still is) a work in progress. I'm not perfect and I don't claim to be. But I do the best that I can and I always remember where I came from and what it felt like to be there.
Hope that helps.