When I used to work for Leonard Bernstein's estate, one thing that came up often was the mispronunciation of his surname. Lots of people pronounce it the way you pronounce Bruce Spingsteen's name, when actually it's pronounced the way you pronounce Albert Einstein's name. Bernstein himself used to correct people by asking, "Well, you wouldn't say Gertrude Steen, would you? You wouldn't say Albert Eensteen, would you?"
But then there are people named Bersteen, as well, who spell it the exact same way Bernstein spelled his name. So how is one to know?
Simple! Follow the German language, which is way more phonetically consistent than ours. You see, most of these names are German in origin, so it makes a lot of sense that we should adopt their spellings and pronunciations. I took German in college, and that set me straight, but if you never studied the language, here's how it goes:
If it's spelled with an ei (like Bernstein), it's an eye sound. If it's spelled with an ie (like Spielberg), it's an eee sound.
Pretty easy to remember, right? None of this silly I before E except after C business (poor height and seize, and all the other nonconformists).
So what about those Berstiens who spell it Berstein, but pronounce it Bernstien? Well, somewhere along the line, between Germany and America, it got bastardized. So they're actually mispronouncing their own names. Shhh. Don't tell.