What basic ingredients should I always keep in my kitchen?

I'm no expert chef, but I find myself in the position of doing the shopping for my wife after work. Usually I need to rely on her for a list of ingredients to get for any recipe we might want to make.

Sometimes though, she's busy throughout the day and can't tell me what to shop for after work. We need to cook more, because we can't afford to just order takeout every time we can't decide what to make for dinner, but because we haven't got a car, making a shopping trip for basic ingredients is always a hassle.

I'd like to keep certain ingredients in stock, so that if we can't make a trip to the store, we can still make a basic meal.

To cut down on the number of things we need to get with each shopping trip, what are some stock ingredients that we can buy in bulk that won't spoil quickly?