One of the most common personal finance rule is the rule of 50/30/20. With this rule, you try to keep your expenses for necessary items under 50 percent and use 30 percent for your wishes and 20 percent for saving. Another good rule is the 80/20 rule, where you save 20 percent of your income and use 80 percent for your all expenses. I think the first rule is better than the second rule because the second rule can lead to higher spending on non-essentials.