Hey M.,
Time outs don't work unless the child understands why like Laura said.
The other Moms will probably not agree with what I am going to say mext - but it worked for me.
You have to find out something that your child does not like. Obviously nothing hurtful or dangerous! Then when she hits etc immediately do the thing to her that she does not like. She will link the two actions and then figure it out.
The one thing my first daughter hated was for me to leave the room without saying anything(especially if we had bee playing together) and ignore her. Also I would tell her "NO" in a stern voice and mean it. Now once she understood the time out thing - oh yes it worked, my middle daughter HATED time outs - so it worked then.
I think some parents have a hard time disciplining their "first born" and wait until it is to late to start re-inforcing it. Rules exist in life so the sooner they start to get that the better for them I say.
I have 3 children only 14 and 15 months apart, so I had to keep some form of order otherwise I would have gone crazy(ier)! Now I am dealing with homework issues!! Oh for the days of hitting, biting and timeouts - LOL.
Challenges are good they help us grow.
M. F