Awesome tips, Ianus. Thanks, I completely agree.

I'm a little more conservative when it comes to utilization; keep it below 10% of your limit.

Also, the whole keeping a balance to incur a little interest is not true! Always keep a small balance during your first billing cycle and when your statement is issued. After, you can go ahead and pay the full balance. That way it's reported on your credit that you are paying it off and reports your utilization.