Quantity: exercise (strength training, cardio or both) at least 30 minutes per day.
Quality: train all major muscle groups (chest, shoulders, back, arms, legs and abs) and include both high-intensity and low-intensity cardiovascular training each week.
Timing: give each muscle group at least two days to recover before training it again.
Habit stacking
Level 1 (Q): exercise at least 30 minutes per day.
Level 2 (Q+Q): exercise at least 30 minutes per day and train all major muscle groups each week.
Level 3 (Q+Q+T): exercise at least 30 minutes per day, train all major muscle groups each week and allow time for recovery.