Attention-Deficit/Hyperactivity Disorder
While some behaviors associated with ADHD are "normal" and not a cause for concern to most people, someone with ADHD will have trouble controlling these behaviors and will show them much more frequently and for longer than 6 months.
Signs of inattention include:
Becoming easily distracted, and jumping from activity to activity.
Becoming bored with a task quickly.
Difficulty focusing attention or completing a single task or activity.
Trouble completing or turning in homework assignments.
Losing things such as school supplies or toys.
Not listening or paying attention when spoken to.
Daydreaming or wandering with lack of motivation.
Difficulty processing information quickly.
Struggling to follow directions.

Fidgeting and squirming, having trouble sitting still.
Non-stop talking.
Touching or playing with everything.
Difficulty doing quiet tasks or activities
Impatience.
Acting without regard for consequences, blurting things out.
Difficulty taking turns, waiting or sharing.
Interrupting others.