What are the early signs of ADHD?

What are some early signs of ADHD? My three-year-old is showing a lot of signs (yes, I know that is really too young to diagnose), but even her doctor is wanting to go ahead and put her in counseling (play therapy) to start working on her anger issues and a few other things she is having problems with. I’m hoping this is just a spell that she will grow out of, but I’m more wondering if there were any signs that anyone noticed with their child at a young age that made you start looking at pursuing getting them diagnosed before they started school.