Listen to or play through a song on your guitar. Identify the sections or parts that repeat.
Choose a portion of the song as the basis for your intro. Refrains are often the part of the song that repeats the most and are an easy choice for intro material.
Remove the vocal part from the section you have chosen. Fine-tune the section. Listen closely to the music and analyze what changes will fit with the song. Leaving out a chord or simplifying the accompanying rhythm are two options.
Select chords, a beat, or a portion of melody that appeals to you.
Experiment with chords or musical material to explore possibilities for developing a song.
String together several short chains of chords, rhythms or melody. A standard pattern consists of some material, a repetition of that music, an addition of something new, and then one more repetition of the beginning material.
Connect the into to the song. For example, a loud intro can lead to a soft vocal section. However, if you begin with a loud intro but do not refer to it again during the song, its initial appearance may seem comical or jarring to the listener. Remember that whatever you choose has consequences for how the song unfolds.