On pure Darwin:
<<The usual way to start it is via 'startx' from the console; that starts both the server and some initial clients like the window manager and a terminal emulator with a shell. Just type in the console:
startx
You can customize what is started through several files in your home directory.
.xinitrc controls what clients get started.
.xserverrc controls server options and may even start a different server.
If you're having trouble (as in, you only get a blank screen or XFree86 drops you right back to the console), you can start troubleshooting by moving these files out of the way.
When startx doesn't find these files, it will use safe defaults that should always work.
Alternatively, you can start the server directly with one of the XDMCP options, like this:
X -query remotehost
Details about this can be found in the Xserver manual page.
On Mac OS X + XFree86 4.x.0
There are basically two ways to start XFree86 under Mac OS X.
1- One is double-clicking the XDarwin.app application in your Applications folder. This will let you choose between full screen and rootless mode in a dialog at startup.
2- The other way to start XFree86 under Mac OS X is via startx from Terminal.app. If you start the server this way, you must tell it that it should run in parallel with Quartz. You do this by passing the -fullscreen option, like this:
startx -- -fullscreen
That will start up the server in fullscreen mode, plus the clients inyour .xinitrc. If the server you have supports rootless operation, you can start it in rootless mode with the -rootless option:
startx -- -rootless>>
Good luck.
Cheers...