How do analysts use ratios to analyze a firms financial leverage? Which ratios convey more important information

Question:

How do analysts use ratios to analyze a firm’s financial leverage? Which ratios convey more important information to a credit analyst—those revolving around the levels of indebtedness or those measuring the ability to meet the contractual payments associated with debt? What is the relationship between a firm’s levels of indebtedness and risk? What must happen in order for an increase in financial leverage to be successful?