A credit is not a normal balance for asset accounts, the purchase account under the periodic inventory system, expense accounts, and the owner's drawing account.
Exceptions to this list would be contra accounts such as Allowance for Doubtful Accounts (a contra account to the asset Accounts Receivable) and Accumulated Depreciation (a contra account to depreciable assets). In other words, credit balances are expected for contra asset accounts. Purchase Discounts and Purchase Returns and Allowances (which are contra accounts to Purchases) are expected to have credit balances.
A general rule is that asset accounts will normally have debit balances. Liability and stockholders' equity accounts will normally have credit balances. Revenue accounts will have credit balances (since revenues will increase stockholders' or owner's equity). Expense accounts will normally have debit balances as they cause stockholders' and owner's equity to decrease.