Tips/advice on how to find someone online?

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I need help trying to track down some people I went to uni with. I know their first names, and I think their surnames. I know they were exchange students from Norway, and a few other bits and pieces. Long story short, I lent them something and I want it back. I've been trying to find them on and off over the past 3 years. But it's gotten to the point now that I am desperate to get it back. The problem is, for the life of me I cannot search for people on the internet. I just don't know how to. Websites and things like that I can find in a flash. Does anyone have any tips for finding people online? I really need help!