I've got a routine down. I plan out a weekly menu each Sunday evening and plan to cook 4 out of 7 days. The other 3 days I figure we'll eat leftovers, go to someones house, or eat out.
Then, I do my grocery shopping on Monday. If I plan correctly, I won't have to go back to the store the rest of the week. (That has not happened yet)
I do not like going to the grocery store without a list, and I prefer to have it broken down by sections in the store. That is where THE ULTIMATEST GROCERY LIST comes in handy. Print it out, check off what you need, and you are on your way.