When booking a bill to Accounts payable, you are Debiting, ? and Crediting ?

Answer 1

When you received goods or services from a supplier and he renders you a bill and you don't want to pay yet, you book in this bill by:
Dr Asset/Expense (depending on what you purchased)
Cr A/cs Payable

When you make payment for this bill, you'd:
Dr A/cs Payable
Cr Cash

Answer 2

You are crediting accounts payable when you are booking a bill. When you pay something on Accounts payable, you then debit that account.

Answer 3

You are debiting the expense or asset account (prepayment, fixed assets, etc.) and crediting Accounts Payable or Vouchers Payable.