FITT

Frequency
Intensity
Time
Type

FITT is general guideline on how often you need to exercise, how heavy should the training be, how long should be the training be & the type of training.

For cardio training.
Frequency: 3 to 5 times a week
Intensity: 60% - 85% of targetted heart rate
Time: at least 30 minutes, work up to 60 minutes gradually
Type: large muscle groups in a continuous & rhythmic manner.

For weights training.
Frequency: 2 to 3 times a week
Intensity: 8-12 reps for general training; 6-8 reps for muscular training; 12-15 reps for muscular endurance training (the weight depend on the number of reps)
Type: Weights in a controlled manner

For flexibility training.
Frequency: 5 to 7 times a week
Intensity: stretch to the limit, but without pain
Time: Hold the stretch for 30 sec
Type: Static stretch

Hmmmm, that should be all.