I went through the same thing. I grew up knowing my mother's family but since my father was born across the country, we never knew them. If you have a last name, try every online resource there is. You can also try an online telephone directory.
I really lucked out and after making a few calls, I found one of my dad's cousins. She was good enough to connect me with some of her family. Though we all live in different states, we have been in touch ever since. I also found a couple cousins on Facebook. Don't be afraid to try. Not everyone wants to make friends...but you'll be surprised at how glad someone might be to find you, too!
it really depends on if the relative is missing. if the relative is missing check Google, Facebook and any other message or ways to communicate with others that will show anything to help if u r just trying to get back into touch try ancestry online it is free and easy I tried it last week and I found where my father was really born.....HOPE THIS HELPS!!!!!!!