Got my Raspberry Pi today. Quickly read a how to get it going, connected it to a computer with a HDMI cable, inserted pre-loaded SD card, attached keyboard, mouse and power and was rewarded with NADA. No video!
Some hunting on the web showed that this is not uncommon. Here is the solution I found:
Specifically I needed to create a file in the root of the SD card config.txt and put in it hdmi_force_hotplug=1
This forces the RPi to assume a HDMI monitor is connected.
I then got the NOOBS setup screen and got Raspidian started.