When you commit a xcode project the first time to your subversion (SVN) or github repository the big question is, wich files or folders can be ignored.
In an OSX project I usually put the both folders
complete to the ignore list. Behind that folder are files like
The image below shows the folder tree of my project Asset Scaler with marked folders that can be excluded from repository.
For an iOS project it's very similar. A discussion on that theme you find on Stackoverflow.
If there are further files that can be ignored don't hesitate to tell me.