If you have no idea who their friends and family members are, and you know their full name, use a free people search like Intelius to look up relatives..then hunt down those relatives.Individual data points don't mean anything unless they can be connected to other data points to make up a person's online presence.
Facebook is the most popular social network, and it has the most robust search engine, so you should probably start there.
Facebook's People Search lets you search for people by filling in one or more search boxes: Name, hometown, current city, high school, mutual friend, college or university, employer, and graduate school.
Open up Google and type in everything you know about the person in keyword format; for example, "sarah los angeles writer tech." Even if you only know their first name, keywords related to their job, marital status, location and school will likely bring up social networks or other identifiable results.
If no social networks pop up in your initial Google search, you may need to go into the social networks themselves.
Even if your registered username isn’t immediately visible in a dating profile, it’s often visible in the URL of your profile, your profile photo filenames, or during communication with other users.
There are plenty of free and paid services which search and monitor social media and email accounts by username. It will rapidly scan popular sites and services for email addresses, usernames, names, and phone numbers to build a comprehensive profile of a person.Once you have several facts about your subject, you'll need to use your brain to make connections and fill in the blanks.For example, if you know your subject's name, job title, and location, you can probably find their Linked In profile.On their Linked In profile, they've probably listed their undergraduate degree and when they graduated from college, which means you can work backward to figure out approximately how old they are.If you can find someone's username, Twitter account, personal email address or You Tube profile, you may have hit gold.You will now be able to display Custom Google Search Results on your Browser.