You've been doing some spring cleaning in your new house, rummaging through this and that, and found a dusty old guitar case that you've never seen before. Is it gold or is it junk? Or maybe the bills have hit you extremely hard and that guitar you bought as a kid, which these days just takes up space in your closet, is starting to give you ideas. Whatever the reason, determining the value of your guitar isn't as daunting a task as it may seem.
Note the model of the guitar, year it was built and the overall condition (mint, excellent, badly scratched, etc.). If you can't determine the year it was built, write down the serial number. With the serial number, you can check sites such as Gibson.com and GuitarDaterProject.org for the date.
Refer to publications such as the "Blue Book of Guitars" (Blue Book Publications). This will give you a good base approximation of what your guitar is worth. Keep in mind that this may not be what you get should you decide to sell, but it will give you a general idea of where to start.
Take the guitar to an appraiser. If you can't find a guitar appraiser online, music stores may be able to point you in the right direction. Some appraisers charge a fee for their services, but can usually provide some form of certificate to substantiate their claim. This method is particularly useful when you know you have a vintage guitar. The appraiser can point out specifics that you missed, such as a rare color, or if your guitar is rare or limited.
Search for your model guitar on the sites eBay, uBid, Craigslist and Music Go Round. Look for guitars similar to yours and record their prices. On auction sites like Ebay and uBid, search for completed sales so you can see how much guitars like yours have sold for. After checking a number of listings, average the prices of items sold, and this will give you a realistic idea of what your guitar will sell for. Many pawnshops use these sites to determine prices (and offer sellers about half of the price items sell for on eBay).
Don't expect that because a guitar is old that its value will be high. Many things are considered, such as condition, color and availability.
When doing comparisons through auction websites (especially for expensive vintage guitars), be on the lookout for look-alikes. Many of these are sold for far less than their authentic counterparts. Remember, if a price looks too good to be true, it probably is.