Once your balance is = to or less than 1/3 of the available credit on that account, it will look the same as being at zero to your Fico score. Meaning if you have a credit limit on card A for $1000 and owe $500, pay it down to $333. Paying it down to zero will have the same effect on your score as paying it down to $333. Apply the remaining $167 to pay down another card. You can expect to pick up a few points this way, but not a whole lot.
It will take about a month after the payment is received for the credit bureaus to reflect your new balances, as creditors submit data on your account to them only once a month.
You can use equifax to pull your credit report and run a fico score on it.
https://www.econsumer.equifax.com/co...landing.ehtml?^start=&orderSource=HPG
Getting an automatic report every time there is a change to your credit file is well worth the money. Its much easier to dispute an error right after it has happened than 18 months down the road.