This is not intended to replace http://www.cavyspirit.com/sociallife.htm#Introductions OR the GL Care Guide in any way. Just some tips that aren't explicitly stated and some reassurances for when your beloved babies start acting like crazed maniacs.
How To Start
-Go somewhere the pigs have never been. NOT the floor time area, even if you've cleaned it with bleach. New place!
-Have things in there that the pigs have never seen. This means you really can't have houses or towels from the cage. Actually, don't have houses at all! Drape freshly washed towels over the corners instead.
-Make the space as big as possible. I blocked off my kitchen. Use a hallway, the entire bathroom, or a pen outside in the shade.
-Load it up with tasty things. You need at least 2 piles of veggies and hay.
Here we are!

See that yellow tube? That was bad- I had to remove it because it caused fights. Those stools were almost an issue too. Really, just food and pigs is good.
Add The Pigs
-Put them all in at the same time! Dont' put one in and then go get the other. That gives them a chance to leave their smells and will set the next pig up to be defensive.
-Follow all the rules from Cavy Spirit for standing ready with a dustpan and separating them if necessary.
Let The Pigs Do Their Thing
-Unless you see blood, they are fine. No, really. So many people want to remove pigs as soon as someone squeals. I'll show you what a MILD intro looks like:
Rumblestrutting!
Max is the black self on the left, then Oliver and Jacob. Jacob is the dominant pig doing the rumblestrutting at both of them. Apparently, if you wiggle your butt and make a *brrrrr* noise it proves that your testicles are the biggest. They're fine to leave do this!

Nose Off!
The pig who gets their nose the highest in the air wins. They might lunge after this, but unless you see blood they are fine. Biting, screaming, hair pulling, are all ok.

The Circle!
Pigs do this to smell eachother's butts or to get in position for some humping. Probably not going to lead to any bleeding, so they're fine to do this all day long!

Humping!
This is a different intro, with Fred and Henry, but here's what it looks like! They can mount any side and they can keep it up for a long time Again, there's not likely to be any bleeding so let them have at it.

Give It Time
-If you don't see blood, leave the pigs there for an hour or more!
-Don't even think of putting the pigs in the house until at least 30min have gone by.
-If pigs aren't exhausted by the end, they've got energy to pick on each other in the smaller cage. Let them get it all out in the big space where it's harder for this to escalate into a real fight.
Here's some MILD stuff that went on in my kitchen for about 2 hours. It wasn't constant, the pigs took short rests for eating and laying down.
Videos so you can hear the noise, see the chasing, and see that they're FINE! :)
Plan old, sniffing, squealing, and chasing.
http://flickr.com/photos/feylin/2631996765/
Mounting, chasing
http://flickr.com/photos/feylin/2631999131/
http://flickr.com/photos/feylin/2631996765/
Fred and Jacob nose off, Jacob attempts to shoot pee, Jacob grooms Max's ear, Max cowers and cries and tries to get away
http://flickr.com/photos/feylin/2631996765/
Max is ganged up on and can't rest
http://flickr.com/photos/feylin/2632808614/
Here's an exhausted Fred at the end.

Give Them A Bath
- If all else fails, bathe the pigs together to remove smells and scare them into forgetting they were fighting.

Prepare The House
-The house should be about 2 grids bigger than the recommended size if you can manage it.
-Clean every single speck of that house. This includes washing the grids with vinegar solution and throwing out anything wood or cardboard.
-You need one more of everything than you have pigs and it all needs to be placed as far apart as they can be.
-NO houses. Drape corners with towels, set up a half loft, use Cuddle Cups. We can't even use sacks.
Put the Pigs In The House
-You need to watch them to be sure the smaller space doesn't cause trouble. Ramps in particular should be watched.

-Weigh the pigs daily. If you don't see blood or weight loss, leave them! You might think one pig isn't getting food or water, but if their weight stays the same they are.
-If one pig has a small weight loss, you can take them out for some extra veggies in a cuddle cup where they feel secure. This should not go on for more than a few weeks. Max needed this.

They're Going To Keep Doing It
- The pigs will have outbreaks of dominance behavior for as long as a month.
-I've had pigs completely trash the cage after 2 weeks of peaceful living
-Keep the pigs a little unsettled by changing locations of food, water, and sleeping spots. You can run the vaccum near the pigs too!
-Take the pigs out for extra floor time so they have some extra room. Doing this in new spaces helps.
-Weigh them weekly and unless you see blood or weight loss, the pigs are fine!
Have you noticed the theme here?
1. You're reducing the chances of a real fight by giving the pigs space and eliminating smells.
2. You're leaving the pigs alone to sort out their social structure. Removing them too early wrecks all the hard prep work you did!
Good Luck! (If any one wants to add to this or sees a mistake, please feel free.)