1. install bzr: sudo apt-get install bzr
  2. copy eOS code branch: bzr branch lp:elementaryos
  3. cd to the dir: cd elementaryos
  4. Edit the config to suite your needs: cd etc && nano config
  5. You can specify the architecture to amd64 or i386, also tweak some things like base or version number (you should leave those as is).
  6. Add elementary daily ppa: sudo add-apt-repository ppa:elementary-os/daily && sudo apt-get update
  7. Go back to the main elementaryos folder and execute ./congrego.sh  it will tell you about required packages. Install them and run it again.
  8. When done builds will be in the builds folder.

This project is putting up builds on sourceforge also if you don’t want to do it yourself > https://sourceforge.net/projects/eosbuilds/files/isis-unstable/

I would try it on a VM because this is pre-alpha software. Also you should report bugs to help development at https://bugs.launchpad.net/elementaryos

note: Reposted from the defunct Tux Fiction blog.