Any useful discussion of acoustic guitar setups should include a close look at the truss rod, the nut, and the saddle. Each of these parts contributes significantly to the way your guitar plays, and each can develop its own set of problems. You can make many of the adjustments I'll describe yourself if you're careful and use a little common sense. If you have a serious problem with your guitar, however, you should not hesitate to take it to a reputable luthier.