If you have a low/mid-price guitar, you can improve things by replacing the standard wiring and potentiometers.
Of key interest here is the pots’ resistance value, because the cheaper they are, the more they tend to vary. As a rule, higher resistance = more treble.
A Strat, for example, can sound very different with 300k or 200k pots (the ‘correct’ value is 250k). Likewise, 300k and 500k pots - both common fitments - sound quite different in a Les Paul or ES-335.
The capacitor in your guitar’s tone control can influence its sound greatly. The lower the cap’s value, measured in microfarads (uF), the less high end will be lost as the tone control is turned down.
So if you reckon your guitar sounds too muddy and it is fitted with a 0.047uF cap, try fitting, for example, a 0.022uF or smaller cap instead. A lower value cap will also make more of the pot’s range useful.
For reference, vintage Fenders had 0.1uF caps - very dark sounding and virtually unusable throughout most of the range of the pot.
3. Treble bleed mod
Standard guitar volume controls can cause a loss in treble when you turn down the wick. That’s because, as a side-effect of altering volume, they act as a low-pass filter (they allow bass to pass but screen off treble).
To get round this, you can do a treble bleed mod. This involves buying and fitting either a capacitor, or a resistor and a cap, wired, usually in parallel, to the pot.
Popular combinations are a 150k resistor with a 0.001uF cap, or 100k/0.002uF. You’ll need a wiring diagram - there’s plenty of these to be found online - and be confident with a soldering iron, too.
4. Loknob Nut Hugga
Ooh-er! Something new here for players that find it too easy to accidentally knock their volume control while playing, but still need to be able to change it on the fly.
The Nut Hugga ($5.99) can be added to your existing 1/4-inch potentiometer under the knob to add resistance and enable more precise setting of the control. See www.loknob.com for details.