Note from the author, Paul Vigna: Cryptocurrencies have become an investing mania again, which means — because I cover the topic for The Wall Street Journal — I field questions from a lot of people I don’t usually hear from. Most recently, a high-school friend I haven’t talked to in years pinged me. He has started investing in cryptocurrencies, but was looking for some guidance.

“Would welcome tips on where to find good info, particularly geared for the newbie,” he wrote.