Start by adding up your regular monthly income, then list essential costs such as rent, bills, food and travel, followed by debts, savings and non-essential spending. Subtract your total outgoings from your income and adjust the figures until the budget is realistic, leaving some room for unexpected costs. Apply it by setting spending limits for each category, checking your bank account regularly and moving money into separate pots if that helps. Review the budget each month and update it when your income, bills or priorities change.