I live by myself and "charge" calories to an account whenever I buy raw foods at the store or eat out. Then, whatever is in my house, I have already "accounted" for in my caloric budget. The strategy comes in figuring out what foods / combinations of foods leave me feeling satisfied. Beans (another great living-alone food, haha) are an allstar. I weigh ingredients for a lot of cooking only so I pace the consumption of rice, beans, etc.

The error in estimation of foods eaten out I treat as a constant factor baked into the daily caloric budget. If I'm gaining weight, the budget just needs to be tightened, i.e. rescaled to account for an error factor that was larger than anticipated. The problem basically becomes estimating one's own estimation error, then adjusting.