Panning audio is one of the most simple procedures in the mixing process. It is so simple because, just like the fader, there is only one control for this entire operation. It is called the Pan Pot. If you have ever done any mixing then you have seen a pan pot before. Whether it be software mixing through a DAW (Pro Tools, Fruity Loops, Cubase) or hardware mixing using a live console. Both of these scenarios will deal with panning audio in the same way, through the pan pot. The pan pot has 2 options: it can be moved Left ( sometimes shown as negative numbers) or it can be moved Right (positive numbers). This is as simple as you might think. Moving the pan pot left moves the selected audio to the left side of the stereo spectrum. Moving the pan pot right moves the selected audio to the right side of the stereo spectrum. What this means is if you are wearing headphones or ear buds and you move the Snare’s pan pot to the right you will start to hear the Snare only out of the right ear bud, likewise if you move the pan pot to the left. If you are panning audio that is stereo in nature you will see 2 pan pots. The left pan pot controls the leftward signal and the right pan pot controls the rightward signal of the audio. If you are confused as to how a stereo track could have 2 audio signals please see my blog covering Mono vs. Stereo sound here: http://www.threepbeats.com/blog/mono-and-stereo/
As I have said before there are no rules when it comes to mixing and mastering but one general observation you may have made is that the Kick, Snare and Vocals are almost always panned in the center, within -5 or +5 degrees of 0. But again there are no rules. I have heard several mixes that break these rules and sound great. You must decide for yourself how you want your mix to sound. That about covers the topic of panning audio in the mixing process. Panning can be a great way to separate instruments that are competing for space and a great way to add width and dimension to your mix.