FIGHTING MULTIPLE OPPONENTS
Now, just to be honest, you should never try to fight multiple opponents. The methods shown here are for you to survive long enough to get out of the area.
Legend:
You - Blue Swirl
Opponents - Red Dots
-The Eight Gates-
There are eight general directions (or "gates") that attackers can come from:

Based on this theory, we can already create a few basic rules for multiple opponent fighting. First, make sure that there are no empty gates seperating opponents.

The closer they are together, the easier will it be to see what they're doing.

Notice what happens when there's an open gate between them. Your attention will constantly have to shift left to right when dealing with each attacker. The more open gates inbetween, the harder a time you'll have.

You can solve this problem by moving in such a way that will make them either occupy consecutive gates, or better yet, occupy a single gate (more on that in a bit). Sometimes, you'll have to keep moving to do this.

Another good solution is by backing up into a wall. Not only does this prevent them from surrounding you, but the closer they get together, the more chances of them getting in each other's way. This will give you the change to use the "human shield" maneuver, or (if you're adventurous) the "human bowling maneuver" (basically, tossing the closest attacker into his buddies).
But remember, these methods aren't foolproof, and you should always, always look for an exit instead of a win when fighting multiple opponents. Unless you know your attackers personally, you will never be able to tell a person's fighting ability until you actually fight them, and miscalculating will result in loss of a limb and a sensory perception (or two).
Some general tips:
KICK LOW
A good stop hit to the leg of an approaching opponent will either stop them in their tracks or cause them to stumble, which will in turn either send them crashing to the ground (if you managed to kick that hard) or into your arms for a grab maneuver that will enable you to employ the "Human Shield"/"Human Bowling" maneuver.
DON'T GROUNDFIGHT
Doing so will invite the other attackers to stomp on you. Should you be taken down, get up as quickly as you can (if you can damage the one who took you down in the process, go for it!).
KEEP IT SIMPLE
Forget the long combos or multi-step grapple moves. Performing one-hit strikes to vital organs or doing a quick one-handed break will serve you far better in this fight, since performing each move successfully will bring the number of attackers down by one.
Take Care!