Add in a reset SW. I once took apart my uncles system and put it back together to find that the reset and power switch were switched D: I found out because the first time I tried turning it on I got nothing. Freaked me out. I checked the power supply was turned on, checked all connections, then decided wth hit the reset switch and luckily it turned on. Don't ask me why they were switched, but in every other mobo I've put together I got the power/reset switch right so my uncles mobo was a weird one...
Oh last mother board I had to reset the cmos to get the thing to boot the first time. Resetting cmos usually involves unplugging the power supply, trying to turn the computer on a few times to drain the charge in the power supply, taking out the small battery on the motherboard, then moving a jumper on the motherboard for a few seconds. You can find better instructions that are particular to your motherboard in the manual that came with your motherboard(my current motherboard I only had to hit a button
).