On OSX Extended attributes are typically just silently ignored or silently work and are no issue. 

Unless you want to tar something... The tarball contains them and can cause issues later.

Initially in OS X you could set the environment variable:
 COPY_EXTENDED_ATTRIBUTES_DISABLE=true

Don't get me started on on the "yes I mean no" problem here... ++ungood...

That stopped working when they changed it to the even more ambiguous
 COPYFILE_DISABLE=true

Seriously? We're not disabling copying, we're disabling copying the extended attributes cruft in normal operations.

You definitely want to add this to your ~/.bash_profile file:

# Make clean tarballs and more in Tiger 
export COPY_EXTENDED_ATTRIBUTES_DISABLE=true

# Make clean tarballs and more in Leopard 
export COPYFILE_DISABLE=true


The "good" news is that that also no longer seems to work and the hunt continues!
For now you can use flags for specific commands:

tar --exclude '\._*' -c -z -f x.tar.gz x
cp -XR x y
COPY_EXTENDED_ATTRIBUTES_DISABLE=true COPYFILE_DISABLE=true make dist