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. But if you don't know anything particularly identifying about the person you're looking for (such as their email address), it's better to skip the fancy search hacks and go straight to plugging in keywords. And it should, because Google is a powerful tool (especially when you know how to use it). It doesn't matter how little you know about the person you're looking for, your search is going to start with Google.
Whether you're looking for yourself or a friend (no judgment), here are five tips for finding out anything, about anyone, online: Plug everything you know into Google. Googling yourself is like checking your credit report for inaccuracies: it's only effective as a preventative measure if you do it thoroughly and routinely. Not because I condone stalking, but because knowledge is power - if you don't know how to find people online, how do you know what people can find about you online? I think everyone should have decent online stalking skills.