Most people don't "get" design. You can hardly blame them: when it works, it's often invisible. Trouble is, that makes designers classic targets for "would you mind creating my entire logo/identity/website for free?" entreaties. (Or worse.)
Still, it can be hard to muster up the courage to tell would-be "clients" freeloaders to go screw. So Jessica Hische has done the work for you, by making a flowchart which handily describes when it's appropriate to work for free.
Here's the part you'll use most often:
Other snake-oil to avoid: "But we're a start-up!" (So's my lawnmower. Your point?) "It'll lead to more work!" (Ooh, more uncompensated labor? No thanks.) "But we're a nonprofit." (No, you're a band. There's a difference.)
Of course, there are some circumstances where you might want to consider working pro bono. Basically, if they're family or close-enough-to-donate-a-kidney-to friends, you should probably cut them a break. (But you don't have to like it.)
Everyone else? Take a number, get in line -- or as Hische puts it -- "MAKE IT RAIN, BITCHES!"