There are loads of things involved with setting up a guitar, and many guitar players - even new, novice guitarists - will have a go at changing a few things to make their instrument more playable.
The most common change - and one of the easiest to do - is to change the string height at the bridge. Often people call this "altering the action"; and while changing the string height will indeed affect the action, there's more to altering the action than simply changing the string height!
Imagine that we're working on a theoretically, perfectly flat/level guitar neck:
With a very low bridge setting, the strings sit very close to the fingerboard. This is known as a "low action". To change the height of the strings, we alter the bridge saddles
With the bridge height raised, the strings are much further away from the fingerboard.
This is known as having a very high action. Generally speaking, most guitarists believe that having a low action is preferable.
A guitar with very high action will be difficult to play. Pressing the strings onto the frets will require a lot more effort and your fingers will tire more quickly. Playing single-note licks and solos is difficult. Bending strings (for that classic signature blues sound) is made hard, as your fingertips snag under other strings as you push them upwards on the neck.
Despite this, high action guitars do have some benefits. For a start, they're louder. If you have a particularly "grabby" playing style, you can play chords without pulling them out of tune. But, generally, a high action on a guitar makes it more difficult to play, and most guitarists seek to reduce the action as much as possible.
But at the same time, it's also possible to have too little action. A guitar has to have some degree of action, to allow the strings to vibrate.
Now guitar strings vibrate in an "ovoid" shape, with the maximum movement at about half way along the string. So while, at first, it seems that a perfectly flat guitar with very low action would be most preferable, to get a "good" guitar set-up, it's actually a balancing act between action height and playability.
The Aiersi kits we got recently are really well made. We put a couple together and made perfectly playable guitars, with the fingerboards held down with nothing more than a bit of double-sided tape! There was no messing about with shims of having to adjust the neck angle or any of that nonsense - simply bolt together, add some strings, and play away!
We lowered the bridge saddles, to make the action even lower, and played a few simple runs. You can hear that although the notes can be played (they don't "fret out" indicating that the fingerboard is, indeed, well made, and perfectly flat) as the strings vibrate, because there's no gap between the string and the next fret, there's a persistent buzz.
Luckily, this problem can easily be solved - but it's one that a lot of guitarists are quite nervous about tackling. Basically, we need to adjust the trussrod.
our fingerboard and neck are perfectly flat
The trussrod is a piece of steel running along the length of the neck.
When the strings are tightened up on a guitar neck, they actually pull the head of the neck forwards, creating a slight "bow" in the neck. The steel rod inside the neck counter-acts against this pulling force.
Somewhat counter-intuitively, a well-set up guitar actually has a tiny bit of "bow" in the neck. This is called relief. Because our guitars are made to be absolutely perfectly flat when assembled, they have no relief in the neck. By adjusting the trussrod, we can reduce the amount of "backbend" used to resist the pull of the strings.
Now it's understandable that, if you're playing around with a thousand-pound instrument, you might be a bit nervous about playing with the trussrod, given that it can have a massive impact on the instrument's playability.
But - then again - if you're trying to play a thousand-pound guitar and the trussrod isn't correctly set-up, you may as well be playing a second-hand, eighty-quid Encore copy!
A lot of websites bang on about how critical the trussrod is to making your instrument playable and how, if you get it wrong, you can render your guitar useless. They're not wrong. But it's not irreversible. And it's not difficult to do. It's scary - especially when it's your best/ most expensive instrument, and the temptation is to take it to a guitar shop and have someone else do it (I know, I've spent £40 to get my Yamaha set up before now, only for it to "settle" a few days later and I ended up with an unplayable guitar anyway!)
Just stick an allan key into the trussrod hole and turn. Give it a quarter of a turn. Leave it for ten minutes or so then try the instrument again (really, you should think about slackening off the strings, adjusting the rod and then re-tuning them but if you've got a floating tremolo, this can be a laborious task!). The strings will be all out of tune. That's ok. Just check that each note can be fretted and doesn't buzz.
Here's our guitar after the trussrod has been adjusted
Remembering that the fingerboard is only held on with double-sided tape at the moment, this is actually a good result! It shows that our neck has a slight "bow" in it (which is why the fingerboard is lifting off slightly, as it tries to rest in a straight line across the two highest points).
Until the fingerboard is permanently fixed, it'll be difficult to play the guitar properly. But by pressing the fingerboard down onto the (ever-so-slightly-curved) neck , we're able to fret notes along its length and demonstrate that each note can be fretted and played without any buzz at all.
And that's how to set up a guitar neck/trussrod!