1. Take a couple of reference dimensions to match the scale of the photograph with the real life object it represents. In this case, it is the overall width and length of the guitar.
2. Draw a rectangle about 3 feet wide and 4 feet high and perform zoom extents. This will give you with a comfortable are to work around.
3. Draw a rectangle that matches the reference dimensions of the guitar.
4. Insert the image. Don't worry about its scale, yet.
5. Use the ALIGN command to both move, rotate and rescale the image so it will fit more closely over the reference rectangle. Adjust the location of the image manually to better fit with the reference.
6. Take advantage of the line of symmetry running through the vertical or longitudinal axis of the guitar. Draw a reference symmetry line.
7. Use the PLINE command to draw the profile of the guitar's sound box, the beautiful curvy shape we want to model.
8. Use the EXTRUDE command to turn this into a solid, 4" high.
9. Use SOLIDEDIT > BODY > SHELL to make the sound box hollow.
10. Create a cylinder and use SUBTRACT command to create the opening.
If I get enough requests, I will create an updated, clearer version.