Quoting Brian Nash (bcnjr5@???):

> Is this the way I am supposed to do it?

Your MUA (mail user agent = e-mail client), even if it's only GMail's
webmail interface, has _two_ distinct reply modes: reply-sender and
reply-all.

o Use reply-all for normal public replies on mailing lists.

o Use reply-sender to send private off-list mail to a post.

Obviously, your MUA will have its own name for those two reply modes,
but those are generic category names.

A few really good MUAs (such as mutt and Emacs GNUS) will automatically
recognise when you are replying to a mailing list and strip
non-mailing-list CCs by default. This is a good idea where possible,
and in some cases (such as mutt) can be explicitly invoked by a 'list
reply' command. But if your software doesn't do this fine-point nicety,
don't sweat it.

Welcome to Internet mailing lists!

On a related matter (an infamous flamewar topic that I will merely point
to documentation about), before anyone brings it up:
http://linuxmafia.com/~rick/faq/netiquette.html#replyto