If you’re relatively new to the freelance game, or even if you’re well-established with a lot to offer, you’ll likely get asked to offer up your services pro bono.
“We can’t pay anything, but it will be great exposure!”
This was my number one warning sign of a sucky client. No matter how much you like doing what you do, you work to make money, and if you don’t respect your own time no one else will either. That said, there are exceptions to every rule, for both rookie and veteran freelancers. So when is it ok to forget the invoice and work for free?