Distortion is very important to guitarists. It's how we amplify the overtones of our instruments, pushing our tone further and further into a technicolor world of richness and vibrancy. Or, to put it another way, it's how we scream our innermost thoughts out into a world in a way that's socially acceptable rather than actually, y'know, screaming.
Distortion can be primal, brutal, beautiful, exciting. And above all, it's personal. There are as many different ways to achieve it as there are guitarists. Think of Eddie Van Halen's approach to gain, compared to James Hetfield's, or Billy Gibbons', or Trent Reznor's. They all have their own unique voice which is made up of a great many parts, and there's no one element which creates a great distortion sound.
Personally, a great many of my favorite tones - my own and those of my heroes - have come about because of how they treat their guitar signal in between them striking the strings and the sound hitting their preamp tubes. There's something magical that happens when those tubes are really given a workout, something you can't achieve by simply adding another tube. So this article is dedicated to those little tricks you can do to get more out of your amp, and more from your voice.
Clean Boost
This one is pretty obvious: if you present your preamp tubes with a hotter version of your signal, it will be pushed into higher realms of overtonal bliss while preserving and enhancing the tone of a guitar that you love, whereas a distortion pedal might get in the way and add its own coloration to your sound. But there's a bit of an art to using a clean boost. For instance, clean boost pedals work great when pushing an amp's clean or crunch channel, and you might be tempted to crank that channel's gain to ten then push it over the edge with a boost. But the thing with analog technology is, it doesn't always work in a way that might seem logical and linear. You might find that with your particular amp you'll get better, clearer-sounding results with a medium amp gain level and a higher boost level. There are also plenty of onboard boosts available which can be engaged via a push-pull pot on your guitar, and this is a great option for those who prefer to rock without pedals. You’ll find this feature in the Les Paul Traditional Pro II, which you can hear in action here:

Overdrive Pedal
Much like the clean boost, this is a pretty popular option - and has been for a few decades - for getting a little more oomph from your tone, but the compared to a clean boost, an overdrive pedal will color your sound a little more. The trick here is usually to use a low gain setting on the pedal, relying instead on its tone and output controls to put some hurt on your preamp tubes. What I like about this method is that you can set your amp for a great rock rhythm tone, then use an overdrive pedal to increase your gain and smooth out your tone - maybe round out the treble and boost the mids - without drastically altering the whole character of your sound.
Adjust Your Pickups!
When I first started playing electric guitar, I had a very, very cheap, nasty plastic distortion pedal which didn't quite have enough gain for the Randy Rhoads tones I was going for. I soon discovered that if I tweaked my pickup height, my guitar put out a louder signal which nudged the pedal over the edge. You have to be careful with this method, because although it might well give you that little bit extra gain needed to realize your perfect tone, if you raise your pickups too far, their magnetic field can interfere with the vibration of the string and cause strange 'wolf tones' - odd oscillations and overtones - and mess with the pitch stability of the note. This is especially true of single coils. And it can work the other way too: When your pickups are lower, the sound tends to be clearer and more defined. So if clarity is a problem for you, try lowering your pickups and then making up the difference with a boost pedal.
EQ Pedals
Here's a method that's often overlooked, but it can really help you to get the most out of your guitar and amp. Use an EQ pedal - graphic EQs can work well, but parametric EQs are better - to find a specific frequency that your amp's preamp tubes respond too, and boost that frequency by just the right amount to get that killer overdrive. This can give you a very clear, punchy kind of overdrive that you can't really attain any other way, because you’re boosting only specific frequencies, rather than boosting the whole signal (which raises the entire level of background noise).
If you use a long cable, you run the risk of signal degradation even if you don't use any pedals at all. This will sap your guitar's high end and reduce its headroom, as well as robbing you of precious signal strength when it comes to gain. So it's a good idea to use a buffer, which provides the signal with a little extra energy to your signal, helping it on its way to your amplifier. A buffer will essentially take cable length out of the equation altogether, which means you can place one right by your amp where it won't be in the way, rather than having to worry about a pedalboard or a buffer on the floor. And some buffers even come with the ability to introduce a slight boost to your signal, which means you can add a little gain if necessary.
What ways have you found to increase your gain, other than the regular distortion pedal or amp channel methods?