Stretch and warm up for 5 minutes before beginning any activity. Exercise at a moderate pace for 20 minutes. Follow with a 5-minute cooldown. Change your schedule to accommodate longer exercise periods when appropriate. Stick to your schedule.
Balanced development is extremely important.
Split your workouts as you become a more experienced lifter. This will enable you to better concentrate on specific muscle groups and areas. Rest your muscles between sessions. Allow each muscle group at least 48 hours of rest between sessions. Your muscles can't grow unless they have time to rest and heal.