If you and your friend had a major falling-out, some of your contacts may not cooperate. It’s worth combing your address book to see if you have written down any connections to them that you have forgotten about.

Search for nicknames as well, even if your friend didn’t have one when you knew her. For instance, an “Elizabeth” might now go by “Beth,” “Betty,” or “Liza. " Search for just the first name, in case your friend’s last name changed with marriage or divorce. On search engines, enclose your friend’s name in quotation marks, then add more information such as the school she went to, the city she lived in, or the business she worked for.

On Facebook, type in a name in the top search bar and hit enter. On the left-hand pane, select People. A list of filters should appear at the top of your search, where you can enter possible locations, workplaces, or schools.

Make sure to scroll all the way through the Pipl results. An email address may be buried in an old blog post, online survey, or forum comment.

Be very cautious with sites that require a credit-card sign up, as they may be scams, or end up being more expensive than you anticipated. All the options above are free. Check your Spam or Junk Mail folder for the confirmation email while signing up.

ZoomInfo’s search is a great resource for people in the corporate world. BatchMates is a free alumni reunion site. It is focused on India but includes members worldwide. If your friend served in the US military, check its online Buddy Finder.

If you do find a marriage record, but no accompanying contact information, you still have the name of a new person to search for (the spouse), as well as a potential change of name to take into account.

Do not be fooled by scam sites that charge you money to search government databases.

You can also pay a few pounds to a private company to perform this search for you.