1. (simplest) Call each CCC and ask when they report. If they sort of stammer around, ask to speak to a supervisor, etc., until you get one who knows what they are talking about.
2. (bit more complicated) MyFICO reports don't show the precise date that an account hits the credit reports, but many credit monitoring services do. I use TrueCredit, which lets me pull daily --so far!-- and both EX and TU show month/day/year on the reports. EQ only shows month/year, as myFICO does, so it's not useful. Also, reports that you pay for directly from each credit bureau show the exact date, as do your free reports from annualcreditreport.com.
In general, most but not all CCC's report on the statement date, when your charges for the previous month, plus any unpaid balance are totaled up. This is different from the payment due date, which comes around 2-3 weeks later. But some cards (and other loans) report at the end of the month, no matter what, and Brammy has one whacko card that only reports her highest balance whenever it happened.
Once you find out the report dates, pay online 4-5 days beforehand to whatever figure you want (paid in full, under 5 or 10%, under 50% if you're just trying to get down maxed-out cards, etc.), and then don't use them again until they post. Once they post, if you did let them report a balance, and you don't want to pay interest, go ahead and PIF before the payment due report.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007