The mod is pretty obvious: Just upgrade to a higher value volume pot in your guitar.  Typically, single coil guitars employ 250k pots while guitars with humbuckers (or a combination) use 500k pots.

Instead, just replace the 250k pots with 500k ones and replace the 500k pots with 1M (i.e., 1000k) ones.  As you might have guessed, the 500k variety are easy enough to come by (including as push-pull pots), but the 1M version is a little more scarce.  However, you can find them on some of the sites listed on the parts links page.

There are two consequences of this modification, and both are advantageous.

First, you add brightness to your tone.  This especially useful on Telecasters since players of those instruments typically want the traditionally "twangy" sound that has a lot of high end to it.  Naturally, you can always cut it back as necessary by simply using your tone knob.  Of course, if you routinely use a muddy tone in addition to the bright one, you might want to similarly upgrade your tone knob to a higher value pot in order to compensate for the extra high end.

Second, your output is stronger.  This is also helpful in guitars with single coil pickups since their output is almost always lower than that of humbuckers.  It's always nice to be able to swap between instruments without having to re-adjust all your volume levels.