Tuning the strings of your guitar to the correct notes is very important. Not only for good sound, you should always practice on a well-tuned guitar so that your ears (read: brains) are always trained to hear the right sound.
In this video lesson, our guitarist Sabin shows you how to tune a guitar into the standard tuning in two ways:
1. using a tuner (absolute tuning)
2. without using a tuner (relative tuning)
Here is relative tuning chart for reference (click for larger image):