Cat in the photo aside - the challenges of shooting a white object in any situation can test even a seasoned photographer. Shooting in any digital format completely complicates the situation for digital is prone to blowing out (losing detail) in hot/white areas. A good rule of thumb - which I learned in cinematography school ( I was fortunate to have learned both digital and film - I went to school just as the digital technology was gaining momentum in the film industry) - that rule is if shooting film it's better to slightly over-expose than under-expose and digital is the opposite; it's better to under-expose than over-expose. Film needs light to make the halides react and capture an image. Over exposed film can be pulled back down. Digital technology's main weakness is the loss of detail if the sensor is over-exposed. It's easier to pull under-exposed digital images up - noting that you're going to get a lot more grain and color artifacts - than to work with an image that was over-exposed because with digital an over-exposed image has NO detail to work with.
I use an incident meter for reading the light in studio instead of my camera's spot meter. The difference between a spot meter (which meters the light reflected from one area of the subject you are shooting) and an incident meter (which reads the amount of light falling on the subject from the light source) - is that reflected light is affected by the color, texture, and position of the object it is read from and an incident meter will give you a general reading of the light all around the subject. This is very handy for lighting a green screen, which must be uniformly lit.
Think of the incident meter as giving you a great average place for your camera settings - to ensure you'll get the best (most "normal") exposure. BTW - "Normal Exposure" is a photography term - an image which is shot with normal exposure will have details in the brightest and darkest areas of the frame. No black shadows without detail, no bright highlights without detail.
Another MAJOR consideration is shadows. You can mask the shadows from the bridge and knobs on a guitar that's stained or finished in a darker color. But white? It's nearly impossible to shoot the image without some shadows (unless the guitar is inside a light box).
By shooting the image with the incident meter I get a medium point for exposure where I won't blow the whites out or get the dark areas too murky - and this makes cleaning the guitar up in Photoshop much easier.
The last thing to consider is the purpose of the photos... if you are shooting them for a catalog, you want straight, clean, non-distorted images. In this application I use a 50mm lens with zero distortion along the edges. I center the lens at 90 degrees from the plane of the fingerboard/neck - and I place the lens in the center of the guitar - usually around 5 inches above the neck/body joint.
If you are shooting images for a magazine (editorial) or a coffee table book - then you may choose to augment the unique design features of the guitar's design. I shot these photos for a book on vintage/classic guitars. For this reason I chose to use the shadows to bring out design details such as the joint between the neck and the body and the "Made in USA" stamp which is gently indented into the wood under the finish on the back of the headstock.
Lastly I chose to use a Panagor Macro Adaptor (it fits onto the camera and the lens attaches to it - it has it's own focus ring and aperture) - to shoot extreme close-up images - macro shots) but limiting focus to a few millimeters. This is called selective focus and it allows you more control over the composition. The human eye - controlled by the human brain - will automatically move to the area of focus in a photograph. By carefully selecting the area that is in focus you ensure the image is presented and received with the content you've selected being the undisputed focal point of the photo.
I hope these little tips help.
Happy shooting! And if you shoot some guitar photos and would like to share them with me, please tag me in your card!