Here is a little table for you
Item - Increase - decrease
Assets - Debit - Credit
Liabilities - Credit - Debit
Revenues - Credit - Debit
Expenses - Debit - Credit
Capital - Credit - Debit (its called drawings)
For example you have paid rent in cash.
Rent is an expense and cash is an asset.
As an expense have increased it will be debited and as an asset have decreased it will be credited.The journal entry will be:-
To Cash - cr
Note the account(s) which comes first is debited and account(s) which come after "To" are credited.
To X -cr
Here we received cash from someone called "X" and we allowed him discount