Writing profiles can be the most fun of all journalistic tasks, because 1) everyone has a story, and 2) almost everyone will surprise you by being much more interesting than you might imagine at the outset, if you ask the right questions.
For some reason, most people will not volunteer or even think of the interesting things about their lives.
The first rule is to do your homework. If it's a regular person, ask for a resume. If it's a public figure, read the previous profiles. (I watched reporters interview Bear Bryant about his life when they plainly hadn't read his autobiography. Very embarrassing.) You never know when a resume will include, "Speaks fluent Japanese" or a similar tidbit, along with basic biographical data.
The second rule is to ask the basic questions: ask about childhoods, parents, brothers and sisters, where they grew up, where they went to school, formative influences, first jobs, summer jobs, turning points in their lives, did they know anybody famous? (Almost everyone did. Dr. Robert Ivy, the Knoxville hand surgeon, roomed at Stanford with the trombone player you see on ESPN ads getting smashed at the end of "The Play" at the end of the 1982 Stanford-Cal game. Could there be a better story than that?)
Don't forget to ask about spouses---and how your subject met his or her spouse. There is always a story to be told.
The third rule is, when appropriate, to remember to ask, "Why?" There is often a reason that is more interesting than the fact itself. "We moved to Missouri when I was 5." Why? Then I switched schools. Why?
The fourth rule is to ask those "hobby" questions: Favorite book? Why? Musical instruments? Many baby boomers play or played in garage bands. Favorite sports? (Golf, tennis, rock climbing.) Other pastimes or hobbies? (Kim Hansard of Mark and Kim In the Morning on Star 102.1 collects toy camels. Why? She has always been a softball 1st baseman -- living in the sand and dust of the infield, so she identified with other creatures of the sand.)
The fifth rule is, when appropriate and possible, call the subject's mother. One of the things that set a New Yorker profile of John McCain apart from many other McCain profiles were the comments from McCain's mother. (The family decided he was going to the Naval Academy just minutes after he was born.) Parents love to talk about their kids, and they'll often tell it like it is.