When you want to increase or decrease an amount in a transaction, knowing whether to use debit or credit depends on the Account code range.
In this chart, the UP arrow means to increase … and the DOWN arrow means to decrease the amount.
Example
On your monthly financial statements, you see that a conference registration (Account Code 553000) was accidently charged to Dues/Memberships (Account Code 510100). To move the expense (decrease) from Dues/Memberships to Conference Registrations (increase), you would credit (-) Dues/Memberships and debit (+) Conference Registrations (553000).