Exercise Routines should be fun!
Having fun is definitely the key to being able to stick to an exercise program. You have to develop one that is good for you...one which you enjoy, is effective, and can evolve over time as your needs change. It can be very difficult to find a routine and get into the groove of things--Here's a site which gives some pointers and things to consider when designing a program specifically for yourself.
Charting your exercise plan is always a good idea. This link is a great example of a healthy exercise plan and how to keep organized and on track.
Flexibility, strength and Cardiovascular training (aerobic activity) are the three main components to an exercise routine. By working to increase your fitness in all three areas you will gain maximum results.
But doing all three only once a week probably won't get you far. Starting with twice a week for about 10 minutes is a good idea. Steadily working your way up to 30-40 minute workouts 4 times a week should be the goal.
It's easy to overstretch or under stretch and both can cause serious injury. Here's a video detailing 6 main stretches good for any workout.