You've got a guitar, but for some reason you're not happy with it. It could be that the strings are too high, or there is bad string buzz on one or more strings, or perhaps you're playing solos and when you go above the twelfth fret the guitar sounds badly out of tune. Whatever the problem, you decide to take it for a 'professional setup'. When the work has been done, how can you tell how well it has been done? Here are a few tips.

If work has been done on the nut, it should hold the strings comfortably: not too tight (gripping the string and causing 'clicking' sounds - especially on the wound strings) and not too big (allowing the string to move around, which may also cause clicks or rattles and cause problems with tuning). The string slots should also not be cut too deep, causing buzzing, nor left too high, causing sore fingers due to excess finger pressure being necessary to fret the strings. In addition, the slots should roughly match the radius of the fretboard. Finally, when playing an open string the string should ring clear. If there is a buzz or rattle the nut has not been cut properly.

Just as important as the nut is the intonation. This should be accurate: for example, if you play an 'A' note on the high-'E' string at the fifth fret then play the same string on the seventeenth fret, the note should simply sound an octave higher. This may be hard to assess, but playing a solo up and down the fretboard should sound in tune and 'musical'.

On a more personal note, the action of the guitar should be set where you want it. The 'action' is simply how high the strings are above the fretboard when none of the strings are being touched. This is a very personal setting, with professional guitarists usually having their own preference.

As a simple rule of thumb, the lower the action the easier the guitar is to play, as less pressure is needed to fret the strings. Due to this 'ease', a low action is usually preferred by players who want to move up and down the fretboard at high speed. However having a low-action may affect the tone and sustain of your guitar. The theory is that the lack of space between the strings and the frets changes the way in which the strings vibrate, although it should be noted that - all things being equal - your choice of pickups and amplifier will certainly have more effect and may determine whether you are happy with the sound. Having a high action should improve the tone of the guitar, and will definitely improve the sustain, but again it is up to you whether the gain is worth the pain of having to press harder on the strings. If you intend to play with a slide, then a high action is preferable, as you will not want the slide to hit the frets.

When you take your guitar back, if all of these aspects are satisfactory, then your guitar may just have benefited from a 'professional-level' setup.