One difference between changing guitar strings on and acoustic versus and electric guitar is that an acoustic uses removable bridge pins to hold the strings in place at the bridge. Bridge pins require a little more fiddling to get them to secure correctly to the string in place at the bridge.
Take it slowly. If you think you haven't executed a step correctly, simply undo what you've done and start over. Nothing you do in stringing a guitar is permanent, even when you crease or coil a string in the process!
After you remove the old strings and pull out the bridge pins, follow this process to restring your acoustic guitar:
1. Drop the ball end of the new string in the bridge hole and replace the pin.
2. Pull the new string until you feel the ball end come up against the bottom of the bridge pin.
Tug on the string to make sure the pin doesn't pop out, but make sure not to crease the string as you grip it for tugging.
3. Insert the string end through the appropriate tuning-post hole.
4. Crease (or kink) the string at the top of the tuning-post hole toward the inside of the guitar (away from the tuning key).
For the three lower (in pitch) strings, kink the string to the right as you face the guitar; for the three higher strings, kink to the left.
5. Turn the tuning key so the string wraps around the post.
For the three lower strings, turn the tuning key so the posts rotate counterclockwise; for the three higher strings, the posts should rotate clockwise. Following this procedure ensures that the strings wrap from the middle of the neck over the top of the post and to the outside of the guitar (toward the tuning key).
6. As you turn the key and wind the string around the post, make sure that the string coils from the top of the post downward toward the headstock surface.
The string may want to flop around as you start to coil the string, so use your other hand to control it.
If you have too much string, you'll run out of room on the post before the string is tightened up to pitch. If that happens, simply loosen the string, pull a little more string through the post hole, re-kink the string, and begin the winding process again.
7. Keep turning the tuning key.
As you do this, the coils around the post tighten, the slack in the string disappears, and the string begins to produce a recognizable musical pitch.
Be sure that the string is inside the appropriate nut slot before the string becomes too taut to manipulate it further.
8. Bring the string up to the proper pitch by turning the tuning key slowly.
9. Clip away the excess string sticking out of the tuning post.
Cut the wire as close to the tuning post as your wire cutters will reach so the point doesn't jab you in the finger! If you don't have wire cutters available, loop the excess string into a circle or break the string by repeatedly bending the string back and forth across the crease.
New strings will continue to stretch (causing them to go flat) even after you tune them up to pitch. To help get the stretchiness out of the string, pull on the string gently but firmly, bringing it directly above the fingerboard, and then tune the string up to pitch by turning the key. After each pull, the string will be flat (under pitch), so repeat the process of pulling the string with your fingers and tuning up until the string no longer goes flat after you pull it. You may have to do this three or four times, but the whole procedure shouldn't take more than a couple minutes.
