According to heplguide.org:
The primary characteristics of ADHD/ADD are inattention, hyperactivity, and impulsivity.
A child with ADD/ADHD's symptoms may be determined by which primary characteristic predominates.
There are different ways of spotting if a child has this condition depending on their age.
Symptoms on each of the three primary characteristics are very detailed and are better not summarized to give you a better light on this matter.
With regards managing this condition or kids with this condition, there are quite positive effects of it that you can actually nurture in them like
-Creativity
-Flexibility
-Enthusiasm & Spontaneity
-Energy & drive
and there are really hard to manage issues about kids that have this condition.
How to help a child with ADD/ADHD by knowing when to seek professional medical advice and treatment, parenting tips and school tips are thoughtfully detailed in this website http://www.helpguide.org/articles/add-adhd/attention-deficit-disorder-adhd-in-children.htm please do check it out :) :)