Assume that you've never seen any of these parts:
Motherboard - unless it's a micro ATX, it can only fit in the case two ways. Micro ATX can fit in the case 4 ways. Once you look at where the rear ports are on the motherboard and where the back of the case is, it's fairly obvious which way it needs to go in. If you don't know that you need to replace the faceplate on the back that comes with the case with the one that comes with your motherboard, that might confuse you at first. Getting it to snap into place can be a pain.
RAM - There are a couple slots it seems like this could fit into, but upon closer inspection, it's more obvious it won't fit into PCI or PCI-E slots. It only fits into RAM slots, and it only fits one way, so if you can't get it to snap in, you can tell you have it upside down.
Optical drive - Depending on your case, you might have to remove the front panel to get it in. Can be a bit confusing. It very obviously only slides in one way though (right side up, tray facing out).
Hard Drive - This can fit into one of two places (HD bay or FDD bay) and it's more obvious that it goes in an HD bay. If you don't think about it, you might put it in backwards, but you'll figure it out you did it wrong when you realize that you're trying to plug it in and you can't get to the plugs. You could potentially put it in upside down, I guess, but it wouldn't matter.
Processor - very obviously only pops in one way; look at the pins and it should be apparent, might have to stare at it to figure it out. Less obvious is the fact that you have to pull the bar up, put the CPU in, and then close the bar.
CPU heatsink - depending on the form factor, it can either go in one of four orientations (none of which are wrong) or one of two orientations (again, neither of which are really wrong). Pay attention to where the CPU fan's 4 pin plug connects to the motherboard and just so long as it reaches, you should be okay. Newbie warning in that sometimes it feels like you REALLY have to apply an assload of pressure to get a snug fit, sometimes you feel like you're going to break it. I could see a newbie getting befuddled/pressured here by the "I don't want to break it, but I can't get it to tighten" feeling.
PSU - can only go in one of two ways. If there's a fan on the bottom, upside down is more obvious (when the fan is pointing the wrong way). The fact that the ***** holes are in more of a trapezoid than a rhombus makes the positioning more apparent. Again, there's only two ways it can fit and if you try to ***** it in the wrong way, you'll figure it out pretty fast.
Video card - there are maybe two places it looks like it can plug into (PCI or PCI-E slot) but upon closer inspection, the PCI-E slot is the correct answer. It doesn't matter which PCI-E slot you plug it into; all of them will work. Don't forget to take the back plates off of the case.
SATA cables - only plug in one way. If it doesn't fit, you're doing it wrong.
Power cables - also only plug in one way. Again, if it doesn't fit, you're doing it wrong.
Mikhalia: and FWIW, my posts are 95% helpful, informative, or funny.
Mikhalia: only 5% or less of my posts are utter crap.
Tyapex: 393 posts of utter crap...
Mikhalia: Sounds about right.