Microphone placement is part art, part science. This is where the engineer really gets to shine. While there are no rules, there are lots of generalities to reference. Basically it breaks down to choices: microphone choice, single or multiple mics, and close or distant placement. Often, the sound of the room will determine how much of it the engineer decides to capture, for instance, a bedroom vs. a large, well designed studio. When acoustic problems are present, close miking is generally called for, although occasionally a quirky room sound is just the thing for a specific track. In a nice sounding room, the engineer has the option of using more of the ambiance, especially on instruments like drums, strings and electric guitars. The great engineers are known as much for their skill in mic placement as for their other talents. Unhappy with the sound? Move the mic before you reach for the EQ. Still unhappy? Try a different mic.