Normally, at what age will you start to notice the signs of an ADHD child?

I've read that you can begin to see signs at around 4 years old, however, I think that's far too ripe of an age. Many medical professionals believe that too many kids of that age are already pretty hyper and overactive. You should probably see a medical professional and request a proper diagnosis, but maybe this article will help you to understand the basics: http://www.webmd.com/add-adhd/childhood-adhd/features/adhd-in-preschoolers?page=2