How would you handle team members using a different OS?

In order to maintain a good workflow for everyone, what would you have to watch out for, and what actions might you take to mitigate any negative effects?

For example: different line endings, editors/IDEs available, etc.

Edit: I should have been more up-front about this post. I'm doing some research for a short presentation on OS agnostic development teams, and what challenges a team might face both transitioning to OS agnosticism and maintaining it. I haven't been able to find any blogs or stories of people who have been through this before (though my google-fu isn't top notch). If you know of any links to a relevant blog post of some sort that would be greatly appreciated as well!