Unfortunately, the numerous links and formatting are stripped out of the HTML and I have no intention of adding them back, but I hope this template helps:
The first thing to check on a dead PC and monitor is that they are plugged in and that there is actually power coming out of the wall socket.
To start out, GmsCool on Eggxpert has a concise checklist that I really like (and I have arrogantly made less concise) for a new build troubleshoot:
Make sure the 4 or 8 pin power connector located near the CPU is plugged into the motherboard (MB) and it is fully seated. Make sure you are not using the wrong (i.e, PCI-E) 8 pin cable.
Make sure the 20+4 pin main power connector is fully seated into the MB.
Make sure the PCI-E 6 or 8 pin power connector is plugged into the GPU video card; if the card has such a connector(s), and that it (they) are fully seated. If this is a modular power supply make sure both ends of each cable are fully seated. If using a very power hungry card and PSU uses split +12V rails, make sure a "single" rail is not being overwhelmed by power demand. [images of various power connectors]
Make sure you used the standoffs that came with the case to mount the MB and not have mounted it directly to the case. [note: Some inexpensive cases use raised nipples in the sheet metal for direct mounts instead which is OK as long as all nipples correspond to mounting holes under the board.]
Make sure you used the rear I/O port panel that came with the MB, and not the one that came with the case. Make sure none of the sharp little tabs have shorted out in the ports.
Try one stick of RAM, and then another. Make sure the RAM is FULLY seated and snapped into place. Make sure the RAM is set in the BIOS at its specified speed, latencies and voltage.
Make sure there are no empty plugs from the PSU shorting out to the case.
Make sure the CPU fan is plugged into the CPU_FAN header.
For a USB keyboard mouse, please plug both keyboard and mouse into USB 2.0 ports (black) not the USB3 ports as USB 3.0 works only after Windows driver is installed.
Is the BIOS set to its default values? Try clearing the CMOS (CMOS reset) with the PSU unplugged from the AC outlet via the MB Manual's or MB Maker's FAQ procedure.
Try an External build (be sure to click "See full content" in JSC's original post), tear it down to a minimal functioning system, lay the main board (helps if speaker connected to front header or embedded on MB for beep codes; or if any diagnostic LEDs, LCD are present) on a piece of plain brown cardboard or other non-conducting surface with only a Keyboard (plugged into a USB2 or PS/2 port), one stick of RAM, CPU, HSF, PSU and monitor to rule out shorts as well as bad components. [Temporarily use onboard graphics if available; otherwise use your video card.]
Switch RAM stick and slot location. Keep seeing if your minimal system works.
If stable, then add one component back to the system at a time. This will rule out components and maybe rule in the defective part. If you have any known working parts that can temporarily substitute this is a good time to try them one at a time.
Often the mere act of pulling the system apart and reassembling it will make a good contact with a previously not completely seated part and result in a functioning system.
Please list all your specific components so we can better assist with your dilemma. [List specific make and model number for every component in system and attached to system and don't forget the case. If this PC is from a major PC builder, list the make, full model and complete model number too. List BIOS version too. Don't forget any parts you upgraded or are trying to install. Links are greatly appreciated as they remove part ambiguity and why should we have to look them up? Be sure to include the full OS version and bit and service pack installed.]
If that fails, this link provides a comprehensive list of what to do when the new PC won't post:http://www.tomshardware.com/forum/26114 ... o-problems
Good planning before buying and assembly hopefully keeps most people from needing this guide. (h/t jimmthang)
Completely dead? No LEDs glowing or fans initially trying to spin? Try the paperclip test on the PSU (testing protocol).