When I'm playing my acoustic guitar a lot, I'll change the strings about every two weeks. It's not necessary to change strings that often if you are just playing around the house, but changing strings a minimum of every couple months would be a good idea anyway. New strings just make your guitar sound better, brighter, and will usually make it easier to play. Just like washing your car makes it seem to run better! LOL, You just feel like you are ready to play better! Old guitar strings do break easier, sound bad, and won't stay in tune as well as new strings either. When you are going to play guitar at a "Live Gig" make sure you have new strings on your guitar and maybe a few extras in your guitar case!
Remove the old strings one at a time. Try to find a place where you can lay the guitar flat or just sit on the carpeted floor. Completely loosen the first string you are going to change by turning the corresponding tuning peg on the top of the guitar, called the headstock. Pluck the string before you begin loosening the tuners at the headstock. The pitch of the note gets lower as you loosen the string.
Once the string has been loosened, unwrap it from the peg and remove it from the headstock end of the guitar. Remove the other end of the string from the bridge, by removing the bridge pin and pulling out the string. If the bridge pins are in pretty tight, you can use one side of a string winder for assistance — slip it under the pin and lift it up. Pliers also work.
Discard the old strings. Using a cleaning cloth, wipe down any areas of the guitar you couldn't reach with the strings on it. Apply guitar polish if you like — you don't get the chance very often.
Line up the new strings on the floor according to the size or gauge. This is to ensure that you put the strings on in the correct order. Uncoil a new string from its package. There is a small ball on the bridge side of the string. Slide the ball-end of the string down an inch or so into hole in the bridge. Replace the bridge pin back into the hole, aligning the carved slot of the pin with the string. Replace the bridge pin, lightly pull on the string until you feel the ball slip into place. If the bridge pin comes back out repeat the process. Begin tightening the string by hand with the tuning pegs at the other end and slowly bring it into tune. If you own a "String Winder," it will come in handy now. If not just keep winding, you will buy one for the next time! They are big time savers. Turn the tuning peg counter-clockwise and make sure the string goes under and over with each complete turn around the tuning peg, this makes for secure fit that is needed to keep the string from coming off or slipping until you have it sufficiently tight and in tune!
Now that the string has been tightened and in tune with the use of an inexpensive guitar tuner, you'll find that pitch will be hard to maintain, unless you take a moment to stretch out the string. Take hold of the string somewhere over the sound-hole, and pull upwards for several times. The pitch of the string will soon drop. Take the time to re-tune the string. Repeat this several times. It actually took more time to write this article than it would to change all of your strings, so go ahead and do all the rest of them at this time. By tomorrow all the strings will be out of tune again, just the tension thing going on. But this time when you repeat the steps from above the strings will most likely stay much closer in tune than today. You should tune the guitar every time you play it anyway and with the tuners available (which are many)it's a breeze and kinda fun too! Man, it is great to have new strings on the guitar! My friends and relatives always buy me strings for Christmas and Birthdays and I always appreciate their thinking of me as a guitar player! Have fun! Finally, use a pair of wire cutters (or an equivalent) to trim the excess string. Snip off the end of the string protruding from the tuning peg. Try and leave about 1/2" of string remaining.
When buying new strings, find the String thickness or gauge which best suits you and your guitar. They typically come in Light, Medium or Heavy gauges. I use Light gauge strings because they easier to hold down and also seem to be a brighter sounding string size! The Brand and of strings and what metals are used in making them is another aspect of personal preference for playability and sound! I use Phosphor Bronze strings which are a brighter sound and made by several companies, I use DiAdario, but there are many choices, see what you like!
Be careful not to stick yourself — the ends are sharp. Do not let someone else tell you what to use for strings, any acoustic guitar can handle Light to Heavy gauge strings and Bronze strings might just suit you better than Phosphor Bronze... You decide for yourself and have fun doing it, right? Again I stress having an order to laying out your strings, especially if you are like me an cut them ahead of time so they aren't so flighty. If you cut the strings first and put them on the wrong site... you can't add more string to them, however you might get lucky and cut a short one long and get away with it... probably not though, lol, it's just the way things work sometimes. So just be orderly and have a plan of attack and it goes faster anyway. I don't want to take a chance with that much string tension being exchanged, that I might possibly compromise my guitar neck! So change your strings one at a time to avoid any problems like that! It's really up to you though. This is just my thoughts on keeping the integrity of the guitar neck intact.