You are taking an inactive body and transforming it into an active body. This process needs respect.
Listening to your body as you move forward is the key. Just remember you're not 20 anymore!
Basics:
1) Do not exercise every day.
Most people who decide to "get into shape" launch themselves full tilt into a program that is not suited to them. This is a great way to build discouragement and low self-esteem. If you think you need a plastic paper thin model to motivate you with some group exercise video - well you better think twice. I promise you the program will be full of highly motivated people who look like they are the happiest people on earth and are probably 20 years younger. These are not realistic role models.
2) Find a buddy
Accountability is one way to keep yourself going. It's the getting started that is often the greater
challenge. Accountability will get you started and keep you committed.
3) Listen to your body, but don't panic
There are no short cuts. It just takes time to tone and strengthen your body. You will be sore now and then. As you get older, your body will complain more too. So push your body a little bit and give it more time to recover. Ideally you will work up to 30 minutes 3-4 x week.
4) Start slow
May I suggest just walking 1 mile once or twice a week? Get your headphones and enjoy some music. Get your dog and enjoy the fresh air. Get your friend and talk while you walk. You will feel so good because you've taken lots of deep breaths and increased blood flow to every organ and cell!
5) Mix it up
One dimensional training will bore you. If the weather is not cooperating, find a sports club that allows drop in classes. These are usually about $10 for an hour. You will meet people and you will do something new. Yoga, Jazzercise, Zumba or open swim. This is a great way to try out a class without parting with a chunk of change.
6) Breathe
Are you going through every day as a "Shallow breather"? Most people do as they get older. When was the last time you counted to 7 to take a deep breath? Your lungs deliver the essential nutrient OXYGEN to your cells and remove carbon dioxide. Next time you take a deep breath - stand up, shoulders back and feel how your body moves. With each breath there is a gentle massage of abdominal organs (stomach, liver, pancreas, kidney, intestines). How do you hold your shoulders? If you are generally hunched then you a squashing your vital organs. They cannot function easily if they are pinched. Notice the difference when you sit up straight.
7) Advance your workout when it makes sense
It took me years to realize that I was pushing too hard too fast. I worked up to a half marathon in 10 months. Nope, hadn't run in a few years - duh. I drained myself so completely that I was shaking and could barely stand after that race. When I tried to exercise after that, my hands would swell and I had no stamina. Of course I had not learned my lesson and was trying to run 5 miles at a pop - after all, I ran that half marathon! Classic. I did not give myself time to recover, I did not listen to my body. I became highly frustrated and quite running for several YEARS.
8) Don't give up!
Since committing to exercising 3x a week, I have worked up to running a few miles at a slow pace. I couldn't do it on the first try or even the tenth. But what I DID do is listen. If I was out of breath or tired, I honored that - and just walked until I felt okay enough to jog a bit more. Sometimes I stopped 5 times - but I knew that moving was better than sitting. It just feels good to feel good.
9) Create motivation
Set a goal that is reasonable and achievable. Is it a 5K run? A tennis match? A Tae Kwon Do belt? It is actually a fun way to get out and see that there are MANY other people are doing this too! You might discover a great friendship!
10) Lift weights
Once a week. Hand held weights are cheap and a great way to start. Strengthen the muscle groups that you don't normally use. You want to develop a balanced body. Yes - ONCE a week! It's amazing how quickly 10-15 curls and overhead lifts can change your muscle tone.
Remember that it takes time to change an inactive body into an active body. I think it will take me about 3 years to make that transition. It is consistency over flash that rules the day. And it will only take you about 20 minutes 3xweek.