Simple troubleshooting (individual things you can try):
Plug charger into the laptop and try booting with that. (Look over to the side to see if the LED battery indicator is on while you are at it)
Hold the power button. Sometimes that works.
Check to know if your laptop is not coming to life at all or if it just isn't booting to the operating system. (if you can get into the bios, that means your system works, but booting into the operating system has issues for some reason that may require further troubleshooting)