When to seek professional medical help

I have been a mom for several years now and at the beginning I felt like I was calling my doctor's office about everything. Which is TOTALLY FINE. They are there to be your resource and simply be available to you. But when do you need real medical help? I thought this article explained this well and was very informative.

Mommy Medicine: When not to go to the ER

When my niece was very young she fell off the couch and was inconsolable. It was late(r) at night, so my sister opted to take a visit to the Emergency Room. She DID THE RIGHT THING, because who knows what could have happened or been wrong. But she just didn't think of calling the after-hours nurse as a resource before doing so and maybe she could have been able to utilize her resources and not had to pay the large emergency room bills. 

What do you think? What has been your experience?