Below are the knobs that are usually found in a guitar:
Fig. A: Guitar Knobs, Volume and Pickups
As you can see, the 2 knobs shown on the figure on the top is actually the Volume and the Tone Knob. The Pick up switch is actually a toggle switch which is used to change which Pick Up sound to use.
Pick up switch can also play a part in shaping your tone. As for which pickup is used best for beginners, I have no preference. However, what I would suggest to beginners out there for this situation is to use the right pickup for the type of song that you're playing. If you play rock/metal sounding music, usually the bridge pickup is used. For mellow sounding songs, the neck pick up (the one nearer to the fretboard) is used instead.
Hope that helps beginners out there.