"Diet and exercise." Those are the usual suggestions.
Fact is that, with exceptions for situations with hours of vigorous activity daily (eg military basic training), a daily routine of stressful exertion of every sort is for building or maintaining functionality for most people but not for fat loss. It doesn't work.
Building strength is another matter. As readers know, for general fitness we like a combination of heavy weight training, "Cardio" of the HIIT type plus some endurance cardio, and calisthenics. That covers all of the basics.
How Hard Should I Work Out? To lose weight? That's not a thing. For general fitness, a hard hour 6 days/week is good.