Are you trying to locate a long lost relative?
Have you looked up the online telephone directory of a town where your family once lived, to find out who might have the same surname as you?
You may be searching for the genetic history of your family and want to know of the experiences of others who share your genes.
Perhaps your parents or grandparents had siblings who were sent to orphanages and you want to know if you have cousins somewhere out there.
Maybe your family was separated by war, or you are the child of a fleeting wartime relationship.
Here are some links you may find useful:
Barnardos Australia - tracing service
Red Cross - tracing service
International telephone and address listings
There are, quite rightly, many privacy issues relating to contact with strangers. I find that the best way to initiate contact is to send a postcard (not in an envelope).
My postcards usually include my email address and post office box, plus the name of a person who may be a common ancestor. It's best just to have two or three brief sentences. I like to have a cheerful but otherwise neutral picture on the postcard, such as a cute animal, beautiful flowers or a colourful bird as that might show that I'm friendly.
Good luck with your own searches!