Asus boards have a led on them, wch indicate weither the mother has power or not. if the LED is on, you're not allowed to remove RAM, or insert a PCI card or so, since the motherboard is still powered.
just like the other suggested. Make sure the PSU is switched on, also make sure your main connector the 20+4 one is plugged in as well as the 4 or 8 pin power connector.
Doing those 3 should be able to get you this. Notice the 4 LEDs. That means the mobo has power like angel said.
If your trying to get the other led's on. You push the little Light Bulb button on the back of the case to turn these led's on. You do this to power down the mobo and install things.