For those of you looking to get started working with quake series of engines, here is the q3map2 wiki with instructions. It is part of GTKRadiant now, the best editor you should be using. For those of you working in Q3/D3 you may want to visit ShaderLab for tips and tools for creating shaders and how to maximize the visual effects these engines are capable of. This is a handy reference to q3map2 shaders. Use Q3ase for a gui tool to create them.
The best place to start mapping for IDTech is here. ALL the info you need to get started.
Hopefully, you found this handy getting pointed in the right direction.