Just thought we should be posting the symptoms since we're putting so much emphasis on how important they are to know. People may experience:
Headache: can be persistent or severe
Whole body: blackout, fatigue, or poor balance
Cognitive: amnesia, disorientation, or mental confusion
Sleep: sleep disturbances or sleepiness
Gastrointestinal: nausea or vomiting
Also common: irritability, mild depression, ringing in the ears, or sensitivity to light

Children:
Older kids symptoms are more similar to adult symptoms.
headache; crying when you move their head around (babies)
drainage, clear or bloody, from the nose, mouth, or ears nausea or vomiting
sudden behavior changes
sleep changes — more or less sleeping
excessive crying
loss of interest in playing or doing their favorite activities
And of course the obvious "giant bump/scrape on their head"

If you aren't sure, go to the doctor. Nothing better than permanent brain damage to spice up life.