Whether your starting our or a seasoned freelancer - where do things go wrong? Need work? Get you frustrated?
For myself (I've been a freelancer for 16+ years): getting clients to deliver what I need to make their project happen on time. I've tried ultimatums, I outline this in proposals and getting started packages and on calls. They pay on time, they just don't get me what I need to do the work on time (since I'm a web designer, I typically need: content, photography, brand information, etc).
What about you?