Great title for this thread
First step would be to disconnect all non-essential components.
Does the motherboard have onboard video? If so, try to boot the PC with only the motherboard, processor and RAM (and obviously power supply) connected. If it works, you can (for now) assume that the culprit is something to do with one of your other components, and by process of elimination, you can determine which. This is not to say that it is the only problem! Sometimes a compatibility issue is possible, which could often be disguised as a defective peripheral component.
If the motherboard does not have onboard video, you could try boot with the abovementioned setup. You obviously won't get any video, but you should hear the characteristic POST *BEEP*, which will tell you that those components appear to be OK. You could proceed from here to plug in a video adapter which should give you video.
If the barebones approach fails, you could try one of several things, depending on the situation.
1) Usually, motherboard manufacturers ship the parts with a "safe" configuration. If you have not changed any jumpers or BIOS settings, you might try switching out components to try ascertain which component is the problem.
2) If you have messed around with motherboard settings (jumpers or BIOS), you might try changing the settings back to default (if you were lucky enough to record the details of the default settings). The BIOS can be reset by removing the battery for a while and then re-inserting it. Jumpers... Well that depends on the motherboard. You should have made a note of the default settings, or you could try google for it. Or ask someone with the same motherboard that has not tampered with the jumpers for their settings. Or you could "rtfm": read the manual. It will tell you what each of the jumpers does (in very broken English, usually), and you can create your own "safe" setup.
