I meal plan, because otherwise I end up forgetting to buy all the ingredients I need and/or forgetting to get a vital component out of the freezer.
Each week I sit down and make out a menu for the week - I usually have some idea what's in the freezer, so will include things from there if I can.
Then I write the shopping list, making sure I have all the ingredients for each meal - I check the cupboards and freezer, to see what I have, and put what's missing on the list.
The menu goes up on the fridge, so each day I can see what, if anything, needs to come out of the freezer for the next day.
I do have a list of meals I cook regularly, and that all or most of us in the family like, and sometimes I refer to that, when I am making the menu, but often I just sit and rack my brains to come up with seven different meals!
I try to make sure that there is a balance, over the course of the week - using different main ingredients (beef, chicken, sausages, bacon, fish etc etc), and a balance between really healthy meals, fairly healthy ones and one or two indulgent ones.
It's made a bit harder by the fact that dh works away a lot, so I have to check if he will be at home for tea, and if he is coming back late, I have to plan a meal that he can reheat when he gets home, plus ds2 and ds3 tend not to let me know very far in advance what they are doing, and whether I am catering for them or not.