The absolute freshest produce is at my farmers' market and it's only open on Saturday mornings, so I buy all my fresh produce for the week then.
My preferred grocery stores for non-produce items are Trader Joe's and Safeway. Luckily they are in the same shopping center, but it's not terribly convenient, so I usually just do one trip per week and try to get everything then.
We keep a grocery list on the fridge (Safeway items on the front, TJ's items on the back) and any time we run low on a staple during the week, I add it to the list right away so that I don't forget to buy it. Then I plan out a week's worth of meals on Friday and add all the ingredients to the various lists.
If I do run low on something or forgot to buy something, there is a Lucky's next to my gym (which I go to every day) so I can just stop in after my workout to pick up whatever I've forgotten. But I hate hate hate Lucky's--every time I'm in there it's a bad experience, how can one store
so much--so I really try to get everything when I do the weekly shopping.