In the Tech Talk forum are two related threads that are seeing a fair amount of action.  The first asks what sort of mistakes you have seen new users make, which is good for a few chuckles, but is also a great way to help you understand the hurdles that those new to the hardware scene will encounter.  The second thread takes a little more courage to post to, as it asks what your own worst mistake(s) were.  Together, these two threads may help a lot of members avoid some incredibly embarrassing situations, so head over and share your stories. 

You can also find a related thread in the HTPC forum, specific to the starting HTPC enthusiast.  There are a lot of choices to make when building one that are very different from the choices one would make building an uber gaming PC, so check out the advice and share any of your tips.

If you are looking for more advanced tips, there is something for you in the Windows forum.  There is a guide to rolling your own Windows install, including all the programs you tend to want to be installed right off the bat.  It is also a incredibly long list of handy programs and links to their sites.