SINGLETON

How to spot: She may or may not be happy about her lack of significant other, but she'll be surrounded by friends and ready for fun.

Tips to take: If you are in a couple, don't be afraid to lone wolf it occasionally - go out without your partner and remember what it felt like not to be a part of a matching set. If you're out together, try mingling separately. You can always share your adventures later.

What to do if it's you: Don't get drunk and hold your own pity party climaxing in a slurred version of I Will Survive on the karaoke machine.
Or if you do, remember one of the great joys of flying solo - you won't have to explain it to your partner afterwards.