I found out someone I know tried to negotiate a raise by talking about how high his mortgage and other bills were. I wish he had talked to me first. That is definitely the wrong approach to take.
Talking about how much money you need is never the right thing to do when you are asking your boss for a raise. Your mortgage and your bills aren't your employer's concern and have little to do with why you should be earning more money. It's not about needing or wanting a raise. It's about deserving one because of what you are contributing to your employer's bottom line.
You earn your salary, your employer doesn't give it to you. Your pay should be based on what you do for the company and what you bring to the table. There is one exception to that rule. There are certain regions where the cost of living is higher and therefore jobs typically pay more. Before you begin to negotiate your salary, you should find out what people working in your field earn in your city.
If you think it's time for a raise, read How to Ask for a Raise. Learn what you need to do before you meet with your boss. Find out how to schedule your meeting and how to make your case. Even see what to do if you get turned down.
Related Article: Dos and Don'ts of Salary Negotiation