I've heard that you need to let meat cool down after cooking before you store in in refrigeration, something about bacteria building up when you do that. Any idea if that's true?
In an ideal world, you would chill any hot food product rapidly before putting it in the refrigerator. However, modern refrigerators can handle the load from a mass of hot food, so it is better to put the food in the refrigerator than to hold it at room temperature to cool.
The goal is to minimize the amount of time in the danger zone (40-140 F, 4-60 C) during which pathogens can grow.
My parents always told me to let things cool down outside the refrigerator before putting them in. There are two reasons for this; avoiding bacteria buildup in the food already in the fridge, and lowering power consumption.
When you add a warm bowl of just about anything to your fridge, the overall temperature in the fridge will rise until the fridge is able to compensate and lower the temperature. The theory (and I would stress that I have not tested this myself) this could increase the buildup of bacteria in the foods closest to the warm substance, as their temperature would conceivably be raised to above four degrees celsius (40 F).
The second point, power consumption, refers to the fact that the internal thermostat in the fridge will activate the engine and coolant pump in the fridge to compensate for the rise in temperature, which in turns draws additional power from the grid.