Before you begin each lesson or practice session you will need to tune your guitar. If your guitar is out of tune everything you play will sound incorrect even though you are holding the correct notes. There is a complete description of how to tune your guitar, at the very end of the book.
The easiest and most accurate way to tune your guitar is by using an electronic tuner. An electronic tuner allows you to tune each string individually to the tuner, by indicating whether the notes are sharp (too high) or flat (too low). If you have an electric guitar you can plug it directly in to the tuner. If you have an acoustic guitar, the tuner will have an inbuilt microphone.
There are several types of electronic guitar tuners but most are relatively inexpensive and simple to operate. Tuning using other methods is difficult for beginning guitarists and it takes many months to master, so we recommend you purchase an electronic tuner, particularly if you do not have a guitar teacher or a friend who can tune it for you. Also if your guitar is way out of tune you can always take it to your local music store so they can tune it for you. Once a guitar has been tuned correctly it should only need minor adjustments before each practice session. To learn to tune the guitar using other methods, see the section on tuning at the very end of the book.