There are no hard & fast rules in this game anymore. It used to be easy: Intel all the way, avoid AMD like the plague. Times have changed.
I have had an equal number of bunk Intel based P3/P4 (i845) machines as I have crappy Athlon (VIA) machines. Hell, I've had compatibility issues with Windows XP and Intel-brand motherboards! That's something I wouldn't have expected just a few years ago.
Research specific motherboards, and take all "reviews" with a grain of salt. Use deja.com to search for any obvious problems, but realize that almost all usenet posts are negative, and it's your job to weed out the morons from those with real cause for complaint.
My current universal PC building rules:
1) Power supply is majorly important. Right now you need at *least* a 300W supply and only buy name brand (e.g. Enermax). Make sure it supports whatever specs will be required by the motherboard/chipset you choose. A good power supply will set you back $50. Don't skimp here.
2) Use only high quality memory. In fact, buy all of your memory from crucial.com , because I'm not sure there's any reason NOT to! Do not use excessive amounts of memory either, 512MB is fine. One stick or matched 256MB sticks will work equally well (this is chipset and motherboard dependent). Right now you'll want a system with either DDR or RDRAM...regular SDR SDRAM (PC133) is waving bye bye.
3) Buy your CPU retail, it's worth the extra $15 for the 3 year warranty and CPU fan. Installation will be a no brainer and you won't have to worry about adequate cooling, etc. The only exception to this rule is if you're going with some ultra quiet cooling solution.
4) The only thing I'll be specific about: nVidia. If you don't want driver issues now or 2 years from now, stick with a video card based on something like the Geforce4 MX chipset. It's cheap, performs well, and the drivers are unobtrusive and frequently updated. I'm speaking statistically here too...while I've had plenty of cards from other manufacturers that have worked fine, I have had nothing but success with cards built with nVidia chipsets since the first TNT came out some 3-4 years ago. In fact I have workstations here that still have 16MB TNT and Vanta cards and for non-gaming/3D application I can't tell the difference between them and workstations with Geforce4 cards, either in performance or driver installation/use.
5) Never buy anything with the intention of overclocking. If you're not a real geek, overclocking is not worth the savings, and makes it very difficult to troubleshoot future problems.
6) There is no substitution for experience. Find a friend who knows what he's doing...preferably one who hasn't just put together one or two machines. I have recommended complete systems by individual components to people in the past, and invariably if they're inexperienced they'll end up with problems...when I know darn well that if I'd set them up personally the machines would run fine. There are too many little things to consider when setting up a machine and maintaining it for the first couple of months...no amount of FAQ's will help
7) DO NOT TWEAK. Never ever "tweak" a machine until you're damn sure it's performing great and is stable. Even then, make sure you have a goal for each tweek, and that each tweek shows a measurable performance gain.
Good luck.
Slackmaster 2000