While I try to keep this script up to date I recommend looking into Homebrew for a simpler solution.
This is bash script to install ImageMagick on Snow Leopard.
Please have a look at install_im.sh to customize your environment.
You can run the script as a normal user, it does use sudo at a certain point, so be sure to not leave the installation unattended. Depending on many factors the sudo command may expire during the execution of the script, so if it asks you again the password don't worry, it's normal.
Alternatively you can run the script as root.
chmod +x install_im.sh sh install_im.sh
If you find that the script uses an outdated version of the requirements or ImageMagick, please modify the script accordingly, test if it can still produce a valid ImageMagick installation and notify me about the changes, thanks.