Find a Person By Phone Number
Before you go to the old phone number, try to use the usual searches first. Put someone´s name into a search engine to see if they come up. Be aware that this can be easy if someone has a less common name. However, if they have something that is very common in the way of names, you may have a lot of results to sort through, which can take a while.
You can also use their name to search for them where many who spend time online are gathering. These social networks are great places to find old friends, classmates, and relatives. Search them by name or even by an email address if you have one. Professional networks are much the same, but used for different reasons. Try to search by name there as well.
If that does not work, and you have an old phone number, you can take that number and do a search in the very same places. You may get a hit on a search engine, or you may find they have listed their number through a professional network. You may also want to try the online white pages reverse search with the number to see if it still comes up with their name. This only works with landline numbers, however.
Those might not work, and probably won´t work with an old cellular number. That does not mean you can´t find them though. You just have to know where to look. You can always try a special reverse phone number lookup that can find those cell numbers that won´t come up anywhere else.