Getting fit, for me, was a very difficult thing to consider. I had not been fit for the majority of my life. But if you really want a change, don't think about how much weight you want to lose, or how you'd like to look. Aim to be healthy. Start by picking an activity you enjoy that you can spend a couple hours a day doing. For me, it was swimming. Everyday before work I would swim for 1-2 hours. On my days off I would swim at least 100 laps. To avoid it becoming mundaine, I would change what type of swimming styles I knew every 5 laps. If you don't have a favorite physical activity, walking or cycling everyday is a good start. Everyone with functioning legs can walk and does nearly every day. So walk a certain distance and gradually work your way up to further distances or greater speeds. Use stairs often. Time yourself to get to places faster. I hate running. I suck at it, but I run is spurts to push myself.
Don't reward yourself with bad food. After any strenuous exercise, you should pick some lean protein to help with muscle gain. If you are vegetarian, or if you prefer veggies to meat, beans like lentils are a great source. Lean meats are things like chicken breasts and salmon. Fish really is great. But before you change your diet, start exercising. Doctors say that you should not change your eating habits and physical output at the same time, because it can send your body into shock. just don't overcompensate your hunger with more food intake, otherwise you're doing nothing good for yourself.
I swam for a month before I started hitting the gym. In my down time I found different exercises to help different muscle groups. Some were with weights, some were with machines, some were with nothing but my own body weight. I tried all types until I was comfortable enough to choose my own work outs. This can also be helped if you get a gym buddy, someone who can push you but also help you find your niche. There are two people exercises that are great for the core and fun while difficult.
Eventually the desire to eat well followed. When i made bad food choices, I forced myself to run around a lake near my house, or get up early to swim more laps. A good way of preparing to eat right is a little internet research on healthy, easy to make meals. Food preperation takes time and can feel like more work than eating out, but preparing a big pot of chili and freezing individual portions can help save money and time throughout he week. Look into freezable, healthy foods.
Ultimately it will be whatever you are comfortable with. Take breaks in between work outs, but no more than a couple days unless injured. The rewards of a healthy life are felt all through the day and once you really get into it, it changes your whole concept of life. Stay on top of it for you and only you. Keep pushing yourself.