Joining the club of your choice is just the beginning. Once you've joined you need to make good use of it.
A great way to get started is to immediately make an appointment with a personal trainer.
A good trainer will talk to you about your goals and health history. Based on this he or she will design a training program customized to your needs followed by a full demonstration of all the exercises. In most clubs there is no additional fee for this service.
Look into the schedule of aerobic or other group training classes. Find out if there are any that interest you. If there are, then try them out. A group setting is motivational and can be very invigorating.
Remember to exercise at your own pace. Don't worry about what others are doing. You don't have to impress anyone but yourself.
Finally, make sure the club offers a variety of exercises. Boredom can set in quickly with the same ole monotonous routine. The trainers at the club can be very helpful at suggesting a variety of exercises for your workout.
"The way to get started is to quit talking and begin doing." ~Walt Disney