Ways to find old friends

Facebook.
Facebook is a perfect place to find old friends. Using facebook you can search for them by there name or email. Or if you know the area they are from or where they live you may also be able to find them by that.

Myspace.
Myspace is pretty similar to facebook. It also contains a huge network of people. Chances are, if you cannot find a friend on facebook they probably have a myspace acount. These are two very popular social networks.

White pages.
Try going to whitepages.com. If you know the area of the person or even an address. You will be able to find them and get their phone number if you like.

Try a mutual friend.
Even if you have lost touch with your friend maybe someone else has not. So if you are close to someone else who knows them, try giving them a call and see if you can find out where your old friend is.

Search online.
Facebook and whitepages are great, but i would also suggest maybe checking search engines or old schools they have maybe attended. The more you look the better chance you will have.