When you first start playing acoustic guitar you may find it hard to get a good sound from it, especially if you are a beginner with soft fingertips. The notes you play will often sound dull and rather stilted and the music doesn't flow nicely. So think about the sound you are creating as you play, try to make at least some of the longer notes sound "sweet", using your fretting finger to add a vibrato effect to the sound. Classical guitarists typically do this by moving their fretting fingers back and forth along the length of the strings whereas blues, rock and electric guitar players tend to bend them by moving them from side to side. It helps if you have access to a recording device of some kind so you can frequently record and listen to yourself playing as you develop the technique. Becoming emotionally involved in the music you play will have a profound effect on your desire to create the variety and quality of sounds which the guitar is so capable of producing. So don't hold back!

The frequency with which you change your guitar strings will vary with your playing style, the cleanliness of your hands during a playing session, how well and how regularly you clean your strings etc etc so there are no hard and fast rules. For sure if your strings start to look discoloured or sound "dull" a change is due, but for most non-professional players - and using normal strings - they should give you good service for between 24 and 36 hours of playing time. Strings with special coatings can extend this time considerably, although you still need to remember to play with clean hands and to wipe your strings and fretboard after each session if you want to get the most from them.