It doesn't matter, as the drainage away from the tank is the key, but you do not want it anywhere near a water well, if you have one. Usually the sides or rear is best location, depending on the terrain. The newer ones with the pump/spray discharge offer more options to location, but front is usually the last place you want a sewer tank of any kind.

I have never heard that the side of the house matters, or the direction, as long as it's in a place where the house drains have to go downhill to the field or tank. Unless you have a pump to send the sewage uphill.

It is usually a straight shot out from the back plumbing wall of the bathroom.

Just as long as it's the rear of the house.