The two main strategies
If you have multiple debts, two main payoff strategies are commonly recommended. The avalanche method: list debts by interest rate (highest to lowest) and direct all extra repayment money to the highest-rate debt while paying the minimum on others. Once the highest-rate debt is cleared, redirect that payment to the next. The snowball method: list debts by balance (smallest to largest) and direct extra payments to the smallest balance first, regardless of interest rate.
The maths
The avalanche method minimises total interest paid. If you have a £5,000 credit card at 24% APR and a £15,000 personal loan at 8% APR, every pound of extra payment directed to the credit card saves more in interest than directing it to the loan. The mathematics are unambiguous.
The psychology
Research by Mochon, Amar and Ariely found that many people experience greater motivation from the snowball method — the faster early wins from clearing small balances give a sense of progress that sustains effort. Several studies found higher completion rates with the snowball method for people who struggle with motivation. Behavioural finance research suggests that psychological sustainability matters as much as mathematical optimality.
Practical steps beyond the strategy
Check whether you can transfer high-interest credit card debt to a 0% balance transfer card (many offer 20-24 month 0% periods with a 2-3% transfer fee). Consider whether consolidating debts into a lower-rate personal loan reduces your total interest burden. And critically: unless you have very high-interest debt, building a small emergency fund before aggressively paying down debt prevents you from running up debt again when unexpected costs arise.