Contracts and Money!
As everyone is aware, I'm a starting illustrator.
I was really lucky to have worked with someone I trusted who I got along swimmingly! I'll write my experience at a later time, but for now, I thought I'll put up other's blogs that I follow here that really helps if you're an illustrator wanting to do some work for people you don't know!
Hire an Illustrator:
Amanda Hall answers really helpful Q And A