Here's some things that have worked for me in my line of work, where I have met my share of "society's finest." OK, I'm in law enforcement and believe Aikido works. We can all "Monday Morning Quarterback" but the best thing is not to get into the situation at all, but once you do:
1. Observe behavior and environment- don't get distracted (cell phones, radios, etc. are your worst enemy in some cases).
2. Look around, be aware- be always vigilant!!
3. Avoid the incident (you never know what people carry, i.e. weapons) or negotiate a peaceful settlement.
4. If you cannot avoid the incident, be prepared to act swiftly and decisively
5. If there's more aggressors than you can take, get out of the pit, don't do the "John Wayne" thing and try to become a crime statistic
6. If it's your life on the line, use whatever there is available to place a barrier between you and the attacker(s) or throw a distraction their way and then get out
7. Don't start anything you cannot or will not be willing to finish
And by the way delivery pizza tastes better than being whacked by Bubba the Thug!!