The 80/20 rule can be implemented in personal finances by focusing on the most impactful areas. This could involve budgeting and savings, where you allocate 20% of your take-home pay to savings and the remaining 80% to expenses. In terms of investment strategies, it could mean focusing on the top-performing assets that bring 80% of your returns. For debt repayment, it could involve identifying the 20% of your debts that account for 80% of your total debt value and tackling those first.