If you can get to grub menu, edit the boot line, adding 'single' somewhere to the kernel options and boot into single user mode.

(somewhere like in http://askubuntu.com/questions/132965/how-do-i-boot-into-single-user-mode-from-grub

The look around. First of all do 'dmesg' to see whether all hardware is up normally.
What I would have do then is to disable graphical regime, so that X is not started, and reboot. Then I should be able to see the console messages
and see whether other than X services started OK. Then start X manually to see if it gets up ...