Don’t panic. And don’t just sit there.
— Try asking their assistants for suggestions of other people who might be helpful.
— If your source is on campus, go see if you can find her or him.
— Try a source database
— Think of a way into the story that doesn’t require comment from the sources you’ve tried. Ask people on the street for their opinion about a topic. Ask them if they’re had an experience with whatever you’re reporting on.
— Gather your string and b-roll
— Spend time smartening up; read more articles about the subject.
In general: as soon as you’ve been assigned a story, start reaching out to sources. Ten minutes spent e-mailing potential sources the night before your story is due could save you hours. Give e-mail inquiries time; not everyone checks their phones as often as you do. Give people you’ve called an hour before calling back, deadline permitting. Explain in your calls and emails that you have a deadline. Make sure you convey your understanding that they are busy, too. You’ll find that if you’re solicitous and polite, your persistence will be rewarded.
A pro tip: BE EXTRA NICE TO ASSISTANTS, ATTENDANTS, STAFF AND SECRETARIES.