Sketch the number "8" (or a snowman, whichever you prefer). Then add straight lines for the fretboard (or neck).

Add form to the base of the guitar and block in the basic parts (the soundhole is the circle, and the bridge is the rectangle). Erase the lines in the neck.

Erase any guidelines you don't need. Add more details, such as the strings, frets (the horizontal lines on the fretboard), machine heads (the bolts on the uppermost part), and the strap.

As you start shading, concentrate on the fretboard strap, shadowed edges of the guitar, and the soundhole. Don’t draw every string going up the fretboard; the viewer's eye will fill them in.