It's a little known fact outside of scoring junkies that all $0 balances reporting on your CRs can actually hurt your FICO score(s). The damage is temporary and once a small balance reports somewhere, then any ding goes away. So, if you are applying for a big ticket item like a mortgage or car, plan ahead and let a small balance report on one CC. If you are trying to edge out every last point, then this is something to consider. There are a few posters in here that expiremented with letting all $0 balances report and the ding can be 10+ points in most cases. Prior to applying for something, it's OK to pay off each account each month because that ding isn't permanent.
You don't have to use cards months. FICO has zero clue what your balances were 2 months ago. It only cares about the current month. So, you can get away with not using the card for months on end. Regardless of use, your CC will still update your CR and it'll still be fully scored. I do recommend using it at least every 3-4 months. Some CCs will close an account for non-use. Just buy a pack of gum or coffee if you didn't want to use it much.
The 30% utilization was put out by some, but IMO, is an incorrect thing to say. It's true that over 30% you'll get dinged. But going from an overall util from 1% to 30% can easily cost you 30-40 points depending on your credit profile. The 30% amount was arbitrarily picked and is considered too high.
Most CCs have a 25-30 day grace period. Yes, pay within 25. There's a former mod on here who suggested paying th eminimum immediately upon receiving the statement and then pay a second payment immediately prior to the statement date to get the balance down to where you'd like it to be. That'll guarantee you'd never be late.
