What are the ways to make payment for credit card bills?

If you have an OCBC debit account as well, you can use your debit card to pay!
It's important to know your billing cycle, so you'll know when the bill will be ready for payment. If you're worried, you can always set a recurring reminder to check your account.
You'll also receive a credit card statement, (mine's by email, I can't remember if that has to be triggered or if it's automatic), but this should serve as a reminder as well. This takes a few days for the bank to process though, but usually, there's quite a lot of time to make payment.
I personally don't like to use GIRO to pay my credit card bills as I like to check through every entry in the statement.

Hey! Congrats on the first credit card.

Remember the golden rule: Always pay off your balance in full!

You can use

1) iBanking to pay off your bills if you have a savings/current account with the bank issuing the credit card. For example, I own an OCBC credit card. I have OCBC 360 account. I can use iBanking to pay off the credit card bill

2) AXS Machine.

3) GIRO

No, you can't use a debit card to pay off the credit card bill. But you can use NETS at the AXS machine.

You will be notified of the bill via snail mail. Most of the time, the bank that issue you the credit card will encourage you to have iBanking service with them. In this case, you will receive the soft copy of your bill via iBanking. Example, I own a UOB card but I don't have any savings account with them. However, I still open iBanking with them so I can receive my bill in soft copy format.

Your credit card bill will have a payment due date. Just remember to pay it as soon as you receive it. Set up calendar notification will be great. Or just pay it off the day you receive it.

Again, the golden rule, always pay off your credit card in full.

Cheers!