Didnt see this on there
When selecting your components be absolutly sure they will all go together, as most component centers have re-handling fees for goods. generally about 25% aswell.
IE dont run out and buy the latest PCI-E graphics card accominied with a cheaper less modern AGP only motherboard.
While building a PC is in all senses very simple, do not take it light heartedly, and remember you will also need fault finding skills, which if its your first can be time consuming for you. Where as a skilled technician can resolve a problem in minutes.
You should also research your select components with some vigour for reliability as opposed to price. Theres many products out there priced so low to tempt you to save some more but they will only let you down.