Using your address book to keep track of people you meet and know
Whenever you add someone to your address book, write down the date and how you met the person. It comes in handy to remember how you know so-and-so.
Anytime you meet people at an event or anything, just pop 'em in your address book, even if you don't have their contact info. The loose contacts you make today might be your next connection down the road. Wow, I sound so marketing-networky saying this, but it's really true.
Even when someone has a new baby, I make an entry in my address book just for that baby. Often I forget the baby names of my coworkers. It's helpful to have their name in my contacts. In the notes field I'll put down "Son of Mary Sue Smith" that way, I can search their record easily.