On acoustic guitars, strings play an important role in the playability and sound of the guitar. On acoustic guitars there are no amplifiers or pickups that contribute to the sound of guitar so strings have a larger impact on the overall sound. The composition and gauge of guitar strings should be considered along with the guitar's body type, when picking out new strings.
Before you get started, take a look at your guitar and determine the type of strings that are used on the guitar. Acoustic steel, electric, classical nylon? Most of the time these strings are not interchangeable. Using steel strings on a guitar that uses nylon strings could cause major damage to the guitar.