The OS X SDL distribution has changed since I wrote this tutorial, so your experience may vary.
Install both the SDL runtime and the SDL development libraries.
Start XCode, and create a new project (file->new project). Select "SDL Application" under the "Application" folder. Click next.
Name the project "gp", and rename the directory to ~/ch01/ and click finish. Let XCode create the directory for you.
Click on main.c and delete it (edit->delete), and delete both references and files when prompted.
Control-click on the project name (under "groups and files") and select Add->new file. Select 'empty file', click next.
Name the file main.cpp and click finish.
After that, you are ready for 02 - SDL Skeleton and Putting Pixels..
Note: if you're new to the Mac OS X platform, you may also wish to read the Appendix A - Releasing on OS X at some point. Don't do it now though - move on to the fun bits first!
Having problems? Try the forums!
Any comments etc. can be emailed to me.