Read, read, read. That's the best thing to do. This cab building stuff can be overwhelming since there's so much information. I know I've combed the web, particularly this site and the wiki, for the last two weeks filling my brain with cab-building info in preparation to start mine. I think getting Saint's book is a good suggestion if you want to get a good basis quickly. I've only gotten a little way through it, but it walks you through the entire cab building and console wiring process and is a nice, easy read so far.
You'll also find that questions like yours are far too open ended. Most of the answers are personal preference and your best way to get those answered would be to review all the projects in the project announcement forum and the projects listed in the wiki.
I've found
RetroBlast to be a great site for reviews to help you decide on what parts to get.
Good luck.