The steps to compile are fairly straightforward in theory but in practise the alt-coin clients I have built so far were forked long enough ago that they have bugs that prevent them from compiling on OSX that have long been fixed in the more popular clients.  Especially on mavericks the compiler is a bit more picky.

Are there any coins in particular you'd like to test a client for?  I've built XenCoin and CinnamonCoin so far.