Recently my Samsung S3 locked up. It was basically dead. I pushed the power button a bunch of times. I pulled the battery, but what I needed to do was combine those two actions.
I found the answer to my dilemma in this helpful troubleshooting guide.
What I needed to do was pull the battery and then push the power button. Pushing the power button while the battery out drains any residual electricity in the phone.
I popped the battery back in and voila, it works again.