Exercises that really target to get most of your body moving is one of the simplest way to get started. I understand that it can be intimidating to enter a gym with all the big equipment. So the best way to start is with a personal trainer. You will be able to learn the proper forms and techniques through a trainer.
Try out fun activities or classes like Zumba and MMA, take your dog out for a walk at the park, play basketball, badminton, or squash. You can also try out one of the free workout sessions with Under Armour at the KLCC Park or Jalan Bangkung Park. I will be there at times to conduct the warm up session and my friends who are all instructors will give you great sessions as well.
How would you define a good workout session?
This depends on what you would like to do and achieve. It is different for all individuals. I prefer to separately tone parts of my body throughout the week, moving to a major muscle group day to day. In order to achieve a healthy body, it is advisable to do a full body workout. You can opt for three workout sessions in a week if you have a jam packed schedule and don't have time to stick to a daily exercise routine.