Method:
List all your debts by interest rate from largest to smallest, regardless of the balance
Work out your budget to make minimum payments on all of them
With your remaining budget pay off the debt with the highest interest rate first
Once the one with the highest interest rate is paid off, then take the next highest and so on
For example: you have a 10k credit card with 18% interest, 1k overdraft with 15% interest and 5k car loan with 3% interest. You would make minimum payments on all three and then pay off the credit card debt first, then the overdraft and then the car loan.
Pros: You pay less interest overall, and you therefore pay off the debt quicker, particularly if you have a large amount of debt.
Cons: Requires discipline allocating money to pay off a specific debt, some individuals lose motivation and skip extra payments minimising its effectiveness. Assumes you can pay more than the minimum balance across all debts.