Planning and preparing for a build
Planning
Read the " The Cathedral and The Bazaar", which is an excellent article describing how the Linux development model works. RepRap is currently almost as excellent an example as Linux in bazaar-style development.
See also What_Tooling_Do_You_Have.
Decide whether to solder the boards, or to acquire them prefabricated.
Tools needed
Depending on the options chosen for parts, one could probably do it with just a shifting spanner or two and a small flat-bladed screwdriver and a medium philips (if you get philips screws) depending on how much you get pre-cut.
A set of drills and a hacksaw would be handy too if you go for less finished part.
If electronics are to be fabricated from bare boards and parts kits, a soldering iron and associated consumables (solder, sponge, wick, etc) will be necessary.