Building a bicycle is a relatively easy thing to do and the experience will inevitably differ based upon the condition of the parts available. For instance, most frames you'll run across will already have a fully-functional crank, fork, and handlebar assembly.
The hardest part of building a bicycle is finding a good frame. Ask around your local bike shop, second-hand sporting good stores, thrift shops etc. Also look for bicycle co-ops in your area that will have plenty of tools and parts for free or cheap.
After you have a good frame, you may have to do one or more of the following (depending upon what's already working and what you desire):
Install a crank. Install pedals. Install front and rear derailers. Install chain. -put long chain on gears to determine chain length -use chain link press to remove excess links -attach chain ends together into a loop using chain press Attach a cassette to the rear wheel. Connect wheel to hub with spokes. -cut spokes to length -attach spokes to hub -insert spokes into wheel -true wheel Put tires on wheels. -install liner on wheel -put inner tube in tire -use tire tool to put tire on Attach wheels to frame. -tighten bolts to allow wheel free movement without being loose -add spacers/washers to axle -add nuts to secure wheel in frame Attach seat post. Install brakes. -Install brake mechanism -Install brake handles -Connect with brake cable
 A lot of people forgo the complication of derailers, cassettes and shifters by opting for a single-speed bike. This involves the use of a fixed (stop pedaling, wheel stops) or a free-wheel (stop pedaling, wheel coasts) cog on the rear wheel. People also do not always use a rear brake. Consider all your options when building a bike, there aren't any rules.
Building a bike is a really fun experience. I hope you enjoy your build and update this wiki with your steps!