List your monthly income, essential bills, debt repayments and savings goals first, then set a realistic limit for the product or service. Compare the total cost rather than just the advertised price, including fees, interest, usage charges, introductory offers, contract length and exit costs. Check that you are comparing like-for-like features and read the eligibility requirements and key terms. For financial products, check that the provider is authorised by the FCA, and leave some spare money in your budget for unexpected costs.