A lot of the things 1 Tanker mentioned will be determined by the CPU you'll use. First, determine your budget. Then how you'll use the machine, again high end gaming, video capturing, editing and encoding, or just basic stuff like the web, word processing. Then decide which CPU you want, if you can afford it regardless of what you're using it for best to get dual core. If your budget allows always best to use a separate video but if you're on a tight budget you can always save by getting onboard video and getting the card later. Decide how many PCI slots you'll likely need, e.g., if you just plan on using onboard sound card, 2 would likely be enough but if you're going to use a separate sound card probably want 3. If you have a camcorder you'll want onboard firewire. It's also best to get a mobo that supports the latest technology like SATA 3.0. Read reviews on this tomshardware and extremetech. I always check out the mfg website to look at the manual and check what their support site looks like. Also can check their forum to see if the mobo you're looking at has any particular problems