As I've been working on Windows machines most of my life I know most of the best practices and apps to keep them secure.
When it comes to security on Apple macs I'm clueless as to where to start.
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I think this webpage is a very good start:
You can download on it several Configuration Guides and Security Configuration Guide for Mac OS X 10.3 (Panther) to 10.6 (Snow Leopard) (but unfortunately right now, not for the latest version 1.7 (Lion)).
The NSA as a very interesting section in their site which is dedicated to security configuration guides for various applications, protocols, and operating systems. In their Mac OS section, they have two PDF guides: hardening tips and security configuration. (Note: the latter PDF link is actually to a PDF hosted on apple.com).