Try sitting down and talking to him about it...Explain to him that it
hurts people when he hits or kicks them..and ask him how he would feel
if someone treated him like that...

lil britches hit and bit me right in front of his pediatrican.
his advice was to bite him back. I sure did! my boy has NEVER EVER
bitten me again. Most times youngins learn this behavior from other wee
ones. Its so frustrating!!!
Next time he does bite him back. As for the hitting stay consistent on
discipline. Get a big roll of duct tape, the key to the trunk of your
car....and WHALLAH!!!! instant peace and quiet from your lil
todzilla!!!!!

One very important key that has not been touched is very simple. aside
from the negative behavior, and trying to correct it (in whatever method
you dem appropriate) MAKE SURE YOU REENFORCE THE POSITIVE BEHAVIOR AS
WELL. This way not only are you showing them what is not acceptable but
they will also learn that life is happoer and more pleasant when the act
appropriately. Yes sometimes this will mean a bribe (although not to be
used often) lol, but believe me it works. My youngest has adhd, and I
had to relearn all my parenting techniques I used with the older cause
they just did not work with him.
And on an aside, yes I do believen in spanking IF NECCESARY. My
definition of necesary though is extreme, like whisper said about the
hot burner. I use it to reenforce the idea that a specific befavior
will result in pain. I am sorry but although I believe in letting kids
take their knocks growing up, they should not have to learn about the
stove the hard way.