How does a lender decide that I'm credit worthy?

When you apply for credit by filling out an application, you normally give permission to the lender to get your credit report from a credit bureau. Lenders use this credit report to work a short-term debt-to-income ratio, where they calculate your present short-term debt payments (excluding your mortgage), and divide the total by your total annual income. Lenders will refuse you credit if your short-term debt is more than 20% of your annual income. The second method lenders use is to add up your monthly bills (not including rent or mortgage and utilities) and divide the total by your gross income (before taxes). With this method, lenders are looking for a ratio of under 35%. 

Next Question:
How does a lender qualify me for credit?

Previous Question:
All my attempts to have an item removed have failed because the lender keeps verifying them.  What do I do next?