I'm a little late on this one, but if you're gonna give people advice on how to get guitar tones, i would keep it as simple and clear as you can.
Everyone has suggested great ways to get amazing tones, but sometimes multiple mics, multiple cabs, multiple amps, etc may not always be practical or possible. What's worse, is if you're getting people with too many mics on a cab with phasing issues and in the end it all just sounds cruddy. Multiple micing techniques in the hands of hobby recordists can be a disaster.
If someone asked me about a hassle free way to get tone, i'd just tell them to take the grill off the amp and place a sm57 an inch off, parallel to the cone, halfway between the dust cover and the edge. Then tell them to move it either closer to the dust cover or the edge to taste. I know this isn't the most pleasing tone to all of our ears, but it's good enough that if the tone coming out of the amp is good, that this mic placement will work and give a decent representation of the amp's tone. The other thing is that i'm sure that most of us are so familiar with the way that 57's act, it's easy enough to eq and mix it so it sounds presentable.
Like i said, this isn't the most ideal way to record guitars, but it yields predictable and decent results.The main point of this mic setup is that it's hard to screw up and it's achievable by even the biggest of idiot. Yeah, i know i'm cursing myself making that statement...
From here, anything that is done can only improve the tones. If they're brave (well, not that brave) they can add a mic somewhere in the room that sounds pleasing. If the people have a nice mic to use, then all the better. If they have decent preamps, yay! If they want to experiment with more mics on the speakers, cool. Just reinforce to them that you need one USABLE track of guitar and the rest is gravy that will be added for flavoring.