All exercises need to be done regularly to be effective. From what I have read, strength training ought to be alternated with higher intensity aerobic exercise throughout the whole week, with maybe one rest day.
Possible warm up (5-10 minutes) include jogging, walking, swimming or cycling. This should be followed by strength training, using bodyweight or dumbbells for 20-35 minutes. Possible strength training exercises using body weight are squat, lunge, crunch, push-up and back-extension. Other exercises like dumbbell press/fly, biceps curl, shoulder press, triceps extension are done with dumbbells. After that, got to stretch for 10-15 minutes.