If you're having a problem with your acoustic guitar, this reference should point you in the right direction to learn whether you can remedy the problem yourself.
Unfortunately, this process isn't as easy as it is on an electric guitar. On an acoustic, to drastically adjust intonation you'll have to re-orient, or replace the saddle. This article details the process.
If it moves, oil it! Simple steps for keeping your tuners is fully working order. Applies to all instruments with tuners.
This article outlines the relatively simple process of adjusting the neck on almost any type of guitar to correct front or back bowing.
You know the really small screws that hold various things (like tuners) in place on your guitar? Overtightening these can cause them to be stripped. Here's what to do if you have stripped your wood screws.
This is a technique used to apply finish to instruments - one that is very labor-intensive, therefore almost never performed. Although this won't provide you with everything you need to know to perform a french polish, it's informative nonetheless.
If you own a well-used guitar, and are experiencing buzzing on certain
frets, there is a chance that fret has been worn down. This article explains the process of correcting that problem.
If you really feel comfortable drilling a hole into your instrument, in order to install and end pin (strap button), then this article should give you the basics. Me... I'll leave drilling up to the pros.
Sometimes, a bridge pin (the thing that holds the string in place on your bridge) can get wedged in, and is very hard to remove. This instructional offers some techniques for extracting these stubborn pins.