How To Change Strings | Step By Step Guide
"Only I can change my life. No one can do it for me." - Carol Burnett

Knowing how to change the strings on your guitar is a definite must-have skill. You cannot rely on someone else to change the strings for you, as they can break at any time, and you can't rely on a guitar tech to come to your house every time you need new strings.
In this lesson, I'm going to show you a very detailed guide on how to change the strings on your guitar and make sure they stay sounding fresh, which will include:
What you need to know before starting, including tools and hardware.
How to remove a string.
How to insert a new string.
You can watch the video below or continue reading for more details.
Even if you have the best strings in the world (if there is such a thing), they will still have to be changed eventually.
How you change the strings on your guitar always comes down to how your guitar is made, especially the bridge technology, and that in turn differs between electric and acoustic guitars.
Change all the strings or just a single/couple?
In general, you'll want to change the whole set, not just a single string. The exception to this is when you are playing onstage with a band and happen to snap a line. For such a situation, you'll want to change that single string, of course.
The reason you want to change the whole set is because you always want all the strings to wear out as evenly as possible. Also, because the actual sound of the string varies as it wears down, you also want the quality of sound to be consistent throughout all strings.
In what order should you change the strings?
I'm not sure if there is any specific advantage to this; probably not, but as long as you change them all it will be pretty much the same. I start by changing the thickest string and work my way down, but that is just a personal preference.
What I do recommend, though, is that you change them one by one. This means:
Remove one string.
Insert new one.
Tune the new string.
Repeat for the rest of the strings
The reason why I recommend not removing all the strings before changing them is that whenever you remove all the strings, the neck of the guitar suddenly has a lot less tension to resist, which means that it will tend to warp back to it's natural shape. If you remove each string one by one, the difference in tension is a lot less, and therefore minimizes this effect. This is the same reason why I also recommend that you tune each new string before moving on to the next one, as tuning each string restores the nominal tension to the neck.
Think of the guitar neck as a spring that resists the tension of the strings: if you remove the tension, the spring will tend to contract. The problem with this is that the neck is much less flexible, and this means that repeated contractions like this can lead to permanent warping or even cracking in some parts.
I've talked with some Luthiers that claim that this is not an issue, and that they've been working with guitars for decades and never had any problem like this with any guitar. Indeed they might be right...but then again, why risk it? Just change them one by one. It will be fine.
What do I need to know before removing any strings?
Where to do it
You don't need any special place to change the strings.
I usually just have the guitar on my lap, but you can also lay it on your bed or just about any table (as long as there's nobody having dinner there).
Tools needed
Depending on you guitar's hardware, you will need a couple of tools to change its strings:
Pliers

You can use a set of quality pliers to cut down the strings to size. Just make sure you don't cut in excess.
You will also need a flat pair of pliers to remove the pins on the bridge of electroacoustic guitars.
Allen wrench

Some kinds of hardware have allen screws that you need to tighten and loosen in order to insert or remove strings. In general, you won't need more than two sizes, although the exact size will always depend on the size of the screws in your guitar. Usually, when you buy a guitar that neeeds allen wrenches, they will come included with it, but otherwise just get the appropriate size.
Yes, size matters.
String winder

This is optional, although it will help you wind the strings faster than doing it by hand, so getting one is not a bad idea (plus, they cost next-to-nothing).
Screwdriver

Always have a screwdriver near. More than one, even better, both flat-blade and phillips.
Rockstars are well known to sleep with a screwdriver under their pillow.
Moreover, I recommend that you get yourself a small toolbox where you can store all these tools, so you don't have to wander around your house each time you need to change a string. I have a small plastic box that serves this purpose just right.

Parts of the string
The strings are fairly straightforward, but you need to know about two parts:

Tip
This is just the plain end of the string. This is the part you'll insert into the bridges and machineheads.
On nylon strings, both ends are plain. Watch out for metal strings, because their ends are quite sharp.
Ball
Metal strings will have one of their ends like this. This ball helps fasten the strings more securely, as the tensions are much higher than with nylon strings. This ball will help lock the string into the bridge or machinehead.
Although fairly similar, the way you change a string always depends on your guitar's parts. You need to look out for two parts that are the most important:
The headstock and nut
This is where we'll find the tuning pegs + machineheads and the nut. The tuning peg is used to rotate the machinehead where the string is wound, to either increase or decrease its tension, and the nut is where the string rests and is the anchoring point from where the string will ring as we play it (the open string).

What you need to do is insert the string through the hole (you can give it a small twist to hold it in place better), and then it will be ready for tightening.
The bridge
This is the other end in which the string is fastened to the guitar. There are two main bridge technologies technologies which will determine how to insert a new string:
Fixed bridge
This is a kind of bridge that holds the strings tightly to the body and is completely fixed, that is, unmovable. I have an Ibanez guitar that has this kind of bridge:

Notice that the strings come off a set of holes in the guitar body, and rest over a piece of metal that is bolted into the body.
This kind of bridge is very stable, which makes it easier to both tune the guitar and change strings, as well as giving a better overall sound to the guitar because the vibrations of the strings are transmitted directly to the whole guitar. However, you lack the flexibility that you have with the following alternative.
Acoustic and electro-acoustic guitars tend to have fixed bridges (I don't think I've ever seen any without one, actually), though they look a little different, as they cannot have a hole to insert the strings from below the body, as they are hollow. My electro-acoustic guitar has this kind of bridge:

In this kind of bridge, the strings are inserted into a hole in the top part, and then wedged in with a pin to lock it in place, while resting on a plastic mount to separate them from the body.
Floating bridge
This kind of bridge technology is great when used with a tremolo bar (which we'll learn to use later on). I have a Jackson guitar that has this kind of bridge:

This kind of bridge in this guitar is known as a Floyd Rose bridge.
If you see carefully, the piece where the strings rest is held by two bolts on the top corners, but there is no fixation on the downside. The bridge is held into place by balancing the tension of the strings with the tension of the springs below the body, as you can see in the following photo.

Yes, I know, that one is another one of my guitars, you can tell by the different color. It's just that the Jackson did not have the back cover removed and this other one did (it's another Ibanez). I'm lazy and I didn't want to remove the cover, so sue me.
Together with the tremolo bar (which is the angled metal arm you can see on the right side on the other photo) you can make the bridge pivot on those two bolts to change the tension of the strings and, therefore, their notes.
This feature of the floating bridge allows to make very cool whammy tricks that are especially common in metal music. The downside to this flexibility is that because there is no hard tie between the strings and the body, the vibrations will not transfer as effectively to the whole guitar, which ends up affecting the overall sound diminishing the sustain. Also, because the tension of the bridge depends on the tension of the whole strings, it usually takes many tries to tune it. Yeah, it takes some time, but it's worth it.
Removing a string
Before removing each string, loosen the tension a bit by turning the tuning pegs accordingly, until you can lift the strings without effort. This will help the strings not snap like a whip when you release them (keeps your eyes safe).
The next step depends on the kind of bridge:
If your guitar has a fixed bridge, you'll need to completely unwind the string from the headstock to remove it, before pushing it into the hole to remove it.
If you have an acoustic or electro-acoustic guitar, you'll need to remove the pins (using the flat pliers I recommended), and then you'll be able to remove the string from the bridge. Afterwards, just unwind it from the headstock.
If you have a floating bridge, you'll have to loosen the screw (you will need to use an allen wrench) that locks the string to release it. After it's free, just unwind it from the headstock.
Inserting a new string
If your electric guitar has a fixed bridge, you'll need to insert the strings from below the guitar body, like so:
