I keep a list of items that we keep in the RV and I go through it before a trip (paper plates, TP, towels, utensils, trash bags, etc.) to see what needs to be replaced.
I add those items to my shopping list.
I have another long list of items to pack from the house (cameras, clothing, coats, dog food, people food, etc.). I use that running list for about a week before we leave and in the morning of the trip. "Purse" is on that list because at the start of one trip I forgot it and we had to drive back home which was 40 miles away. Husband was not happy. I cross off the items that are packed and circle the important ones.