You should also actually USE your credit cards. Having open credit does nothing for your credit report.
Use it once monthly and pay the entire balance to build a long history of succesful credit use.
Best thing to do with credit is...If you don't have the cash and you need something... Ensure that you can pay 90% of the item at your next billing date...and then the other 10% the month after. If you can't... Then you probably should walk away.
Cars and homes are obvious exceptions. Not everyone can fork over cash for either of these items up front. Credit is a necessity for some.
As long as we have credit in this country... The poor/ignorant (those who can't manage their money and live paycheck to paycheck) will continue to be poor and the rich (those who own credit companies and can manage their own finances) will continue to get richer.
A person's credit history is also a good indicator of their intelligence.