Spend Based on Your Income
We all know people that spend way above their means. Blame it on credit cards, expensive tastes or whatever you want, but spending more than you can afford is a huge problem that leads to debt.
Credit cards are just a way to make you spend your money, and even more than you should, because of the interest charges. They're a double-edged sword, so they have to be used carefully. Remember your income will still be the same, and you'll have to pay credit cards after all. That's why your expenses always have to be based on your income, so you can be sure you can afford them, otherwise, you'd be at the risk your accounts become negative.
Most of the time this kind of expenses are recreational or for personal taste, for this reason it may not be evident at the time, but it's really important to consider it could be a bigger problem later.
If you choose to use your credit cards or make a large expenditure, always keep in mind you must pay it as soon as possible or in an organized way.