IRC screen cap someone took of me, regarding recording electric guitar:

" first you need at least two mics and hopefully a console, at least some sort of summing system, and mic pre's with a phase reverse, or if you use extreme ghetto technology, a out of phase cable and an in phase cable.
lets just say that you are doing heavy barfing death palm muting stuff for this so you dont want much room sound, just big chunk, so when you stop playing it stops....this will work for a bigger with room sound too, but this is for example.
I say that stuff so I can say for this example, just two mics, on a 4x12 one mic on axis right into the center of the cone, one mic on a different speaker, off axis sorta, pointed at almost the surround, but still inside the speaker

Ok now, make some sort of steady noise, hum ( easy if you have a fender strat) or maybe put your guitar near a VGA monitor, or even just plug a tone generator into the amp now bring up the first mic ( i am assuming a console for this, tailor to youer needs as necessary). turn it and the gain till you got zero of some sort on your meter, just from the noise.

now leave the first mic fader where its at, but hit the mute for that channel

now bring up the other mic on fader # 2 till it is at zero

now turn on fader one( unmute) see if the levels drop as if they are out of phase, if not hit the phase switch till it looks out of phase so the level drops set it so that the faders are out of phase for sure, and make sure they are at the same level

now, cancel your health insurance, tell everyone around DO NOT TOUCH the guitar or tone generator or whatever... put some headphones on that hear the two faders ( like control room mix to your headphones) go out in the room with the amp make sure the headphones are so loud you dont hear the amp direct, only the mic'ed signal

now you should hear a hum or tone or whatever noise you are sending in your ears in your headphones

now move the mics back and forth relative to each other, and you will hear phasey, flangey whooshing noises

at some point, they will be SO out of phase that you will not hear JACK in your headphones...stop right there and rejoice

now go back out to the console and flip the phase switch to opposite what it was you now have a " theoretically " in phase guitar mic setup!

it will be fat ass and shit, you can push the faders back and forth now that you know theyre in phase and all

use the faders as your primary eq, the two mic piositions will be different enough that you will get a wide range of sounds just by pushing them

also as a variation on this, the phasing trick works best at the frequency of the tone you sent it...it is most accurate at that frequency, thus if you are most worried about a certain part of the tone, you can use a tone generator to send that frequency, and phase using that...

You can make for a bigger, more room, sound and still be in phase-ish as you are phasing the mics, just keep moving back away from the cab, you will hear it get louder and softer, in cycles. After 1 or two cycles, you will probably have to turn up the mic preamp gain at the console, as the mic being further away will bring it to less than zero.

you can use more mics, different mics, whatever, just be aware that phasing will be a little less between unmatched or more mics...but youll figure it out

Also once you are done, you can stick the tracks in a PC editor multitrack app and line the phase up even more! You may think to just throw two mics up and phase them in your app later,

!!!!BUT it is EASILY possible to have two mics in phase, but have them in places that DONT sound good. Better to have a good idea first of how it will sound!