Some great comments so far!
I’ve periodically worked in (and out of) photography for decades now. Now I do more film/video work, but not as a cinematographer or gaffer (lighting person). But I work on capturing images, and more importantly, this is the internet. So of course I have thoughts. Short version: There’s a lot to getting consistently good images of any object, especially something with the mix of color, and detail as a fine guitar. But there’s lots of good info available that will get people going. Lots and lots and lots; too much. The key thing is to narrow our search.
Basically, I’d start by doing a Google search on "Product Photography Tutorial”
Product Photography Tutorial
Alternatively, search on “Tabletop photography”
That tends to focus on objects smaller than guitars, but with eBay, Reverb, etsy, and the rest, lots of people are sharing pretty decent advice on what to do. This book, now kinda hard to find, takes a nice approach; the writer assumes you don’t have tons of photography equipment, but still want good results. Note the guitar on the cover. It’s an electric guitar, and a clear one at that. But hey, close enough, huh?
One great thing about photography tutorials: You can check the results to see if the tutorial is worth following. :-) Here are two that look decent.
This is a six-minute video from B&H, sort of the Sweetwater of photo and video equipment. But they’re not making a hard sell. A couple of their ideas involve using paper towels do diffuse your light… Kinda along the lines of Karan’s technique. The video shows someone photographing a watch (something even smaller than a uke), but some basic concepts are quickly described.
This page and video is also decent, and talks about using free to cheap stuff to control light.
Product Photography – On a Budget
Photography is fun, but not as fun as building guitars. ;-)
HTH!